neba-15 Add lazy loading support to fields referencing other resources
neba-15 Add lazy loading support to fields referencing other resources

 - Added Apache License Header
neba-15 Add lazy loading support to fields referencing other resources
- Improved Handling of Optional declarations and added nesting support
- Removed usage of anonymous classes for callbacks
- Improved test coverage and inner structure of FieldValueMappingCallback
neba-15 Add lazy loading support to fields referencing other resources
 - Improved javadoc
 - prepared next release version (3.4.0)
Merge branch 'feature/neba-15' into develop