first adaptation to OpenEntity API 0.21.0-SNAPSHOT

- todo: IEntityService.searchEntities, IKnowledgeService.searchConcepts
- todo: SearchResult is too etype oriented, should be generalized
Merge origin/master

Conflicts:
	src/main/java/eu/trentorise/opendata/disiclient/services/EntityTypeService.java
	src/test/java/eu/trentorise/opendata/disiclient/test/services/TestEntityTypeService.java