Update ``.gitignore`` to ignore local user generated media.

This is located in ``/media/``.
Amend ``MEDIA_ROOT`` to upload files at the root of the repo.
Add FormSet to add extra imagery to the application.

https://github.com/madewithbytes/us_ignite/issues/80

The images can be added as in the edit application
page.

This is handled via a ``FormSet`` the max number of
images is ``10`` at the moment.
Add ``ApplicationImages`` to the app admin.

https://github.com/madewithbytes/us_ignite/issues/80

An inline admin form has been added to manage any
uploaded asset associated to an app.
Make sure the image field is always present.
List extra imagery in the ``Application`` detail page.

https://github.com/madewithbytes/us_ignite/issues/80

Any extra imagery is listed in the app profile page.