Made store product images be stored in media/store/products

Before, they were being stored... well, everywhere: in
static/images/store, avatars/, store_images/, but they were actually
being loaded from avatars/. We had a route set up in webstore/urls.py
that loaded up the images from avatars/, but this introduced an
arbitrary file viewing exploit.

So, that route has been removed, and we use Django's built-in
media-serving static route feature to set that up.
Removed unused file webstore/views-back.py

(Presumably this was a 'backup' used somewhere, but never removed.)
Made companion fabric images be stored in media/companion/fabrics

Previously, they were one of the many things stored in avatars/. I also
removed the getImage view from the companion app's views.py, since it
should (in theory?) no longer be necessary.

I was not able to test this commit because of the currently-unfinished
state of the companion app. However, I followed the same general
principles as the commit that moved the store product images, so it
should be OK.
Removed getImage view (and the route leading there) from frontend/views.py

I couldn't find any place this view was actually used, and it was broken
(security hole/wouldn't work if the server wasn't started from the right
directory), so I have removed it. If I'm wrong, this commit can be
reverted.