[2.0 Spec] Java generator: Implement Enums #287

 Very basic implementation
 [2.0 Spec] Java generator: Implement Enums #287

 Very basic implementation
 [2.0 Spec] Java generator: Implement Enums #287

 Unittest
Merge pull request #294 from martoe/287

 [2.0 Spec] Java generator: Implement Enums #287