Moved Classes Retrieval SPARQL Query to  config.js.
Removed unused functions from Endpoint Services.
Merged AvailablePropertiesService into EndPointService.
Changed retrieval of Classes and Properties to be working as "real" promises.
Removed useless baseURL
Improved UI of Subject Addition, Retrieval of properties and Subjects.
Merge branch 'feature/refactor-endpoint-services' into develop