[FEATURE] refactored sidebar

__Tasks:__
- [x] done
- [ ] got feedback

__Informations:__

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| Tests pass?   | -
| Fixed tickets | -
| Doc           | -

__Requires:__
- https://github.com/sulu-cmf/SuluSalesOrderBundle/pull/14
a constant / template for the url would be nice