Introduce abstract (DAO/CRUD) services

AbstractDaoService and AbstractCrudService can be extended to provide easy DAO/CRUD access.
Web controllers use new service api.
Adapted webapp archetype to use the CRUD service.
Remove unused import
Removed illegal Table annotation.

The Table annotation is illegal because the Inheritance strategy for the Application hierarchy is SINGLE_TABLE.
Merge pull request #26 from buehner/service-improvement

Improving service tier with abstract DAO/CRUD services