* add parent_id field to namespaces table to store relation with nested groups
* create routes table to keep information about full path of every group and project
* project/group lookup by full path from routes table

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Apart from Issues and Merge Requests pages, there are other sort/filter
dropdowns that needed updating.

Signed-off-by: David Wagner <david@marvid.fr>

Updated fork page UI

## What does this MR do?

Updates fork page to new UI.

## Are there points in the code the reviewer needs to double check?

:confused: 

## Why was this MR needed?

'coz new forks page looks awesome, that's why!

## What are the relevant issue numbers?

Closes #17810.

## Screenshots (if relevant)

![Screen_Shot_2016-07-07_at_03.43.45](/uploads/d4be046d1a6b043f3691633b7ec396c6/Screen_Shot_2016-07-07_at_03.43.45.png)

[youtube video](https://youtu.be/YpXPCxWGCnY)

## Does this MR meet the acceptance criteria?

- [ ] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry 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 [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [ ] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !5007