Initial migration to django-rest-framework

* The ajax back-end now runs via djang-rest-framework
* Most JS rewritten to accomidate backend change
* Breaks:
    * Server entry details display, e.g. player list,
    server location map, connect button, etc.
    * Preference-based ordering
    * > < tags are broken client-side
    * Favourites being highlighted
* REST interface for adding/deleting favourites not implemented yet
* Server model now has custom manager with search() method which
implements 'tag-based' filtering
* Client-side: URL hashes are now interpreted as a list of comma
seperated tags and are appended to the search field's tags

Introduces static/js/serverstf.js which is now the main lib for
interfacing with the REST service. api.js and search.js are no
longer used but remain in hte repo for now.