APIService: Use APICalls externally

This allows us to define what is in an APICall without being forced
to conform to Intents. Eventually APICall is serialized and put
into an Intent so everything can be accessed by the Service.
Fix image upload
Fix image delete

http-request didn't allow sending a body with a DELETE request so
we decided to include the imageids as part of the URL.
Fix OpenID login

This involved creating a new endpoint for retrieving info about the
currently logged in user.
API: Remove unused Context parameter