[FEATURE] media ui

Merge this Pull-Request beforehand:
- https://github.com/sulu-cmf/SuluMediaBundle/pull/6 (Media-Manager)

__Tasks:__

- [x] overlay for adding collections
- [x] detail view on click on title
- [ ] gather feedback for my changes
- [ ] submit changes to the documentation


__Informations:__

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| Tests pass?   | yes
| Fixed tickets | none
| Doc           | none