Merge pull request #75 from dejan-brkic/master

Asset Service Implementation
Merge pull request #76 from dejan-brkic/master

Finalize asset service and merge refactoring.
Merge pull request #77 from dejan-brkic/master

Descriptor Service and REST controller
Merge pull request #78 from dejan-brkic/master

ContentTypeService; TemplateService
AssetService implementation unit tests