Docker file cleanup
Docker file cleanup

- Bump nginx to 1.12.1, as the 1.7.x series is full of CVEs!
- rpi-update & boot config changes don't make sense inside a container
- Debian supports C.UTF-8.  Use that so we don't force location settings
  on a user.  This is also a built-in locale, so we don't need to regen
  locales.

nutechsoftware/alarmdecoder-docker