Add "API" to all API docs

doc/api/access_requests.md

-# Group and project access requests
+# Group and project access requests API
 
  >**Note:** This feature was introduced in GitLab 8.11
 

doc/api/award_emoji.md

-# Award Emoji
+# Award Emoji API
 
 > [Introduced][ce-4575] in GitLab 8.9, Snippet support in 8.12
 

doc/api/boards.md

-# Boards
+# Issue Boards API
 
 Every API call to boards must be authenticated.
 

doc/api/branches.md

-# Branches
+# Branches API
 
 ## List repository branches
 

doc/api/broadcast_messages.md

-# Broadcast Messages
+# Broadcast Messages API
 
 > **Note:** This feature was introduced in GitLab 8.12.
 

doc/api/build_variables.md

-# Build Variables
+# Build Variables  API
 
 ## List project variables
 

doc/api/ci/lint.md

-# Validate the .gitlab-ci.yml
+# Validate the .gitlab-ci.yml (API)
 
 > [Introduced][ce-5953] in GitLab 8.12.
 

doc/api/ci/runners.md

-# Runners API
+# Register and Delete Runners API
 
 API used by Runners to register and delete themselves.
 

doc/api/deploy_key_multiple_projects.md

-# Adding deploy keys to multiple projects
+# Adding deploy keys to multiple projects via API
 
 If you want to easily add the same deploy key to multiple projects in the same
 group, this can be achieved quite easily with the API.

doc/api/deploy_keys.md

-# Deploy Keys
+# Deploy Keys API
 
 ## List all deploy keys
 

doc/api/enviroments.md

-# Environments
+# Environments API
 
 ## List environments
 

doc/api/groups.md

-# Groups
+# Groups API
 
 ## List groups
 

doc/api/issues.md

-# Issues
+# Issues API
 
 Every API call to issues must be authenticated.
 

doc/api/keys.md

-# Keys
+# Keys API
 
 ## Get SSH key with user by ID of an SSH key
 

doc/api/labels.md

-# Labels
+# Labels API
 
 ## List labels
 

doc/api/members.md

-# Group and project members
+# Group and project members API
 
 **Valid access levels**
 

doc/api/merge_requests.md

-# Merge requests
+# Merge requests API
 
 ## List merge requests
 

doc/api/milestones.md

-# Milestones
+# Milestones API
 
 ## List project milestones
 

doc/api/namespaces.md

-# Namespaces
+# Namespaces API
 
 Usernames and groupnames fall under a special category called namespaces.
 

doc/api/notes.md

-# Notes
+# Notes API
 
 Notes are comments on snippets, issues or merge requests.
 

doc/api/notification_settings.md

-# Notification settings
+# Notification settings API
 
 >**Note:** This feature was [introduced][ce-5632] in GitLab 8.12.
 

doc/api/pipeline_triggers.md

-# Pipeline triggers
+# Pipeline triggers API
 
 You can read more about [triggering pipelines through the API](../ci/triggers/README.md).
 

doc/api/projects.md

-# Projects
-
+# Projects API
 
 ### Project visibility level
 
@@ -17,8 +16,6 @@ Constants for project visibility levels are next:
 * `public`:
   The project can be cloned without any authentication.
 
-
-
 ## List projects
 
 Get a list of visible projects for authenticated user. When being accessed without authentication, all public projects are returned.

doc/api/repositories.md

-# Repositories
+# Repositories API
 
 ## List repository tree
 

doc/api/repository_files.md

-# Repository files
+# Repository files API
 
 **CRUD for repository files**
 

doc/api/services.md

-# Services
+# Services API
 
 ## Asana
 

doc/api/session.md

-# Session
+# Session API
 
 ## Deprecation Notice
 

doc/api/settings.md

-# Application settings
+# Application settings API
 
 These API calls allow you to read and modify GitLab instance application
 settings as appear in `/admin/application_settings`. You have to be an

doc/api/sidekiq_metrics.md

-# Sidekiq Metrics
+# Sidekiq Metrics API
 
 >**Note:** This endpoint is only available on GitLab 8.9 and above.
 

doc/api/snippets.md

-# Snippets
+# Snippets API
 
 > [Introduced][ce-6373] in GitLab 8.15.
 

doc/api/system_hooks.md

-# System hooks
+# System hooks API
 
 All methods require administrator authorization.
 

doc/api/tags.md

-# Tags
+# Tags API
 
 ## List project repository tags
 

doc/api/templates/gitignores.md

-# Gitignores
+# Gitignores API
 
 ## List gitignore templates
 

doc/api/templates/gitlab_ci_ymls.md

-# GitLab CI YMLs
+# GitLab CI YMLs API
 
 ## List GitLab CI YML templates
 

doc/api/templates/licenses.md

-# Licenses
+# Licenses API
 
 ## List license templates
 

doc/api/todos.md

-# Todos
+# Todos API
 
 > [Introduced][ce-3188] in GitLab 8.10.
 

doc/api/users.md

-# Users
+# Users API
 
 ## List users
 

doc/api/v3_to_v4.md

-# V3 to V4 version
+# API V3 to API V4
 
 Since GitLab 9.0, API V4 is the preferred version to be used.
 
@@ -65,7 +65,6 @@ Below are the changes made between V3 and V4.
 - Return 202 with JSON body on async removals on V4 API (`DELETE /projects/:id/repository/merged_branches` and `DELETE /projects/:id`) [!9449](https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/9449)
 - `GET /projects/:id/milestones?iid[]=x&iid[]=y` array filter has been renamed to `iids` [!9096](https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/9096)
 - Return basic info about pipeline in `GET /projects/:id/pipelines` [!8875](https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/8875)
-- Simplify project payload exposed on Environment endpoints [!9675](https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/9675)
 - Renamed all `build` references to `job` [!9463](https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/9463)
 - Drop `GET /projects/:id/repository/commits/:sha/jobs` [!9463](https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/9463)
 - Rename Build Triggers to be Pipeline Triggers API [!9713](https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/9713)
@@ -81,11 +80,4 @@ Below are the changes made between V3 and V4.
   - `GET /projects/:id/repository/blobs/:sha` now returns JSON attributes for the blob identified by `:sha`, instead of finding the commit identified by `:sha` and returning the raw content of the blob in that commit identified by the required `?filepath=:filepath`
   - Moved `GET /projects/:id/repository/commits/:sha/blob?file_path=:file_path`  and `GET /projects/:id/repository/blobs/:sha?file_path=:file_path` to `GET /projects/:id/repository/files/:file_path/raw?ref=:sha`
   - `GET /projects/:id/repository/tree` parameter `ref_name` has been renamed to `ref` for consistency
-  - `confirm` parameter for `POST /users` has been deprecated in favor of `skip_confirmation` parameter
-
-#### EE-specific
-
-- Remove the ProjectGitHook API. Use the ProjectPushRule API instead [!1301](https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/1301)
-- Removed `repository_storage` from `PUT /application/settings` and `GET /application/settings` (use `repository_storages` instead) [!1307](https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/1307)
-- Removed `elasticsearch_host` and `elasticsearch_port` from `PUT /application/settings` (use `elasticsearch_url` instead) [!1305](https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/1305)
-- Make approval API more RESTful. Use `POST /projects/:id/merge_requests/:merge_request_iid/unapprove` to unapprove a merge request. [!1518](https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/1518)
+- `confirm` parameter for `POST /users` has been deprecated in favor of `skip_confirmation` parameter