Starting work for the backend to act as a REST API for a SPA frontend.

api.py is a set of views, that return jsonified versions of the models.

Updated urls to add the new functionality under /api
1st version of the API implemented. Calendar creation still missing.

Still not convinced about the routing. DegreeSubjects is difficult to place anywhere, really.
Added Yeoman scaffold for new SPA HorarisPompeu GUI.
Updated angular resources
Added documentation for the REST API
Merge branch 'rest_api' into develop
Updated requirements
raw_entry is a reado-only field on edit mode