EZP-20930: Added missing ressources links

* application/vnd.ez.api.Root:
  - /Root/contentByRemoteId
  - /Root/contentTypeByIdentifier
  - /Root/contentTypeGroups
  - /Root/rootUserGroup
  - /Root/locationByRemoteId,
  - /Root/locationByPath
  - /Root/objectStateGroups
  - /Root/objectStates
  - /Root/globalUrlAliases
  - /Root/createSession
* application/vnd.ez.api.ObjectStateGroup:
- /ObjectStateGroup/ObjectStates
* application/vnd.ez.api.Content:
  - /Content/ObjectStates
* application/vnd.ez.api.ContentType
  - /ContentType/Groups
  - /ContentType/Draft
* application/vnd.ez.api.Location:
  - /Location/UrlAliases
* application/vnd.ez.api.User:
  - /User/Groups
Merge branch 'feature-EZP-20930-REST_root_resources'