Added comment service.
Merge remote-tracking branch 'origin/jpa' into jpa

Conflicts:
	ld-content/src/main/java/de/hska/ld/content/config/ContentConfig.java
	ld-content/src/main/java/de/hska/ld/content/service/CommentService.java
	ld-content/src/main/java/de/hska/ld/content/service/impl/CommentServiceImpl.java
	ld-content/src/main/java/de/hska/ld/content/service/impl/DocumentServiceImpl.java
* Added transactional to service methods.
* Fixed tag tests.