Add self to item notification

@thraxil this PR adds the AJAX notification status UI checkbox.

Other stuff in here:
- A few JS libraries have been updated (jquery, backbone, underscore, typeahead). I did this in order to use backbone-relational, but that turned out to be unnecessary.
- I moved all API urls into the API project. This made it necessary to convert a few ad-hoc api endpoints to django-rest-framework. The biggest change was that the projects search feature now uses django-rest-framework's search filtering.