[FEATURE] Register Content Types by DI tags

- Refactored content type manager to accept alias => service ID
  registrations.
- All content types must now use the `sulu.content.type` tag.
renamed compiler pass
Merge branch 'develop' of git://github.com/sulu-cmf/sulu into feature/content_type_tags
cleanup
Merge pull request #142 from sulu-cmf/feature/content_type_tags

[FEATURE] Register Content Types by DI tags