Establish API endpoint for instance clusters

Specs test correctly now

Get, post, put, delete

Add get, post, put, delete API support and specs
Remove extra blank line
Remove extra new line
Add changelog entry
Add API docs for instance cluster
Add post, put, and delete
Add specs for get and post
More specs for get

Add specs for put and delete

Add specs for put and delete instance clusters, fix linting

Add documentation for instance cluster API

Add documentation for how to CRUD instance clusters via API, in the
process of documenting also tested that curl requests work

Git rebase with master

Need to rebase because behind master by a lot of commits, this was
failing doclint tests

Accidentally pushed a merge conflict

Address MR review comments

Fix docs and changelog, add specs and params

Address MR review comments

Add clarity to docs and changelog, add some specs, more api
parameters

Address remaining MR comments

Remove extra new lines

Add a spec to ensure no project clusters

Fix relative link

Actually fix the relative link this time

Put instance cluster API in admin module

Move instance cluster code and specs to admin module

Add a spec for multiple instance clusters

Added a spec for multiple instance clusters, also moved some specs into
the valid params context since they had valid params.