xml template improvements

xml template improvements, taged properties (rl controller), title property

__Tasks:__

- [x] test coverage
- [x] gather feedback for my changes
- [x] submit changes to the documentation
- [x] implement property title (translation keys) in content form
- [x] change ResourceLocatorController in ContentBundle
- [x] property access with tags
- [x] content title in form property access
- [x] adapted Tags form generator template (https://github.com/sulu-cmf/SuluTagBundle/pull/31)

__Informations:__

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| Tests pass?   | no => https://github.com/sulu-cmf/SuluTestBundle/pull/10
| Fixed tickets | none
| Doc           | https://github.com/sulu-cmf/docs/blob/master/detail-specification/300-webspaces/DET-301-template-architecture.md