[WIP] Rewriting TreeBrowserBundle docs

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | yes
| Applies to    | all
| Fixed tickets | part of #262 

 - [x] Classes?
 - [x] Structure?
 - [x] Examples?
 - [x] Standards?
 - [x] Reference Config?
 - [ ] Understandable?
 - [x] Advanced topics?
 - [x] Text?