update static media paths
update requirements.txt; track licenses
add/rm symlink to ddr dir on USB HDD when mounting/unmounting

We don't know in advance what the name of the USB HDD will be
We don't want to store that in a settings file bc we don't want
to make our users have to edit that file.
Nginx needs to have a stable file to use for /media/.
So, symlink to /media/USBHDDNAME/ddr when mounting.
rm some XML-isms; clean up links
rm python-virtualenv from .deb dependencies

We're not going to try to install inside a virtualenv.
It's too complicated and ddr-local is intended to be installed
as the only app on an appliance-like VM.
calculate file.url when loading from JSON

file.url is used by sorl.thumbnail
shuffle settings.py; keep better track of redis DBs
sorl-thumbnail

- Using Redis caching and ImageMagick/GraphicksMagick
- Added to entity detail and file templates