Merge branch '24903-allow-groups-with-special-characters' into 'master'

Allow dots in group names to pass validation for Create Group and Edit Group forms

## What does this MR do?
Allows dots within group names to pass form validation when creating or editing a group.

## Are there points in the code the reviewer needs to double check?
Nope, pretty straight forward.

## Why was this MR needed?
Although group names with dots are allowed, our frontend validation mistakenly invalidates them

## Screenshots (if relevant)

#### Before:
![Screen_Shot_2016-11-23_at_4.55.03_PM](/uploads/006ee5f694de1c98e0df0b0ccd3807ee/Screen_Shot_2016-11-23_at_4.55.03_PM.png)

#### After:
![Screen_Shot_2016-11-23_at_4.52.42_PM](/uploads/693f112fb309005b0df714b32c99f25e/Screen_Shot_2016-11-23_at_4.52.42_PM.png)  
![Screen_Shot_2016-11-23_at_4.51.53_PM](/uploads/7bdb5fca92995d18a7f38d9150eb260c/Screen_Shot_2016-11-23_at_4.51.53_PM.png)  

## Does this MR meet the acceptance criteria?

- [ ] ~~[Changelog entry](https://docs.gitlab.com/ce/development/changelog.html) added~~
- [ ] ~~[Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)~~
- [ ] ~~API support added~~
- Tests
  - [ ] Added for this feature/bug
  - [ ] All builds are passing
- [x] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if it does - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?

Related to: #24622
Closes #24903

See merge request !7723

app/views/shared/_group_form.html.haml

@@ -13,8 +13,9 @@
       .input-group-addon
         = root_url
       = f.text_field :path, placeholder: 'open-source', class: 'form-control',
-        autofocus: local_assigns[:autofocus] || false,  pattern: "[a-zA-Z0-9-_]+",
-        required: true, title: 'Please choose a group name with no special characters.'
+        autofocus: local_assigns[:autofocus] || false, required: true,
+        pattern: Gitlab::Regex::NAMESPACE_REGEX_STR_SIMPLE,
+        title: 'Please choose a group name with no special characters.'
 
     - if @group.persisted?
       .alert.alert-warning.prepend-top-10