Move entire app structure over to using the new config system.

Move entire app structure over to using the new config system.

This is a huge change!  This means several things.

 - From the python point of view, launching the application is a heck
   of a lot cleaner.  You just need to pass in the config file path to
   MediaGoblinApp's __init__() and whether or not this funtion should
   setup celery and you're good.
 - There are now two separate config files, separating the server
   setup from the application setup.
   - server.ini: the paste deploy config file, which configures the
     applications and server setup but *NOT* the mediagoblin application
     itself.
   - mediagoblin.ini: where you configure mediagoblin (and possibly celery)
 - Launching the application is now different.  Instead of:
     ./bin/paster serve mediagoblin.ini --reload
   We launch like:
     ./bin/paster serve server.ini --reload