Init / Namespace / Workdir

Build failed when work directory was missing. New init method
ensures existence.

Moved work directory to /var/cache because /tmp gets cleaned
on reboot.

Renamed registry namespace to match other names
Added upstream image cache support

Initia caching that simply pulls an image through the docker
registry services (mirroring) and pushes it out again. The pulled
images get tagged to the base name.
Improved image name handling

By initially parsing the image name we do not need to check and
re-parse it all over the place