Removes old web interface code
Adds initial django project structure

This is a little different from the regular django project structure. To
acomodate our pypln.{backend,web} packaging manage.py was moved one directory
up.
Activate admin app
Adds basic Corpus and Document models
Adds Django REST Framework

This commit adds an API to list, create, update and delete Corpora
Adds document list to the corpus serializer
Adds Document serializer and views
Adds fixture with two users and one corpus for each
Requires authentication in the corpus list view
Adds login url for api
Filters listed corpora based on the current user
Rename the CorpusList view test class
Adds basic authentication to the GET method in CorpusDetail view
Adds basic auth to the GET method in DocumentList view
Adds basic auth to the GET method in DocumentDetail view
Adds some tests for the creation of new Corpora
Renames corpus FK field in Document model
Adds new tests for the modification of corpora
Adds some tests for document creation
Restricts the corpus choice based on the current user