Displays full name with username in competition views

Fixes siggame/webserver#5.

* Changes the users to be displayed as Full Name (Username) if a fullname is available.
* Added a search box to help people find free agents:
    * Added javascript to the free-agent view to use bootstrap typeahead
    * Added piston views (and urls) to access the competitors which includes api endpoints to list all users, all users for a competition, all free agents for a competition, and search views for each.
    * Added an overload to the CBV to redirect to only result if search results in only one competitor.
    * Created a utility.py for the functions generating the filter for the user set.
* Added a template tag to do the display name for this feature and used it