make: turn ubuntu docker into template
This allows us to easily add more ubuntu docker targets (which following
patches will do).
Also, we no longer need the mkdir command.
FROM ubuntu:__CODENAME__
RUN apt-get update && apt-get install -y \
build-essential \
debhelper \
dh-python \
devscripts \
python \
python-all-dev \
python-docutils \
zip \
unzip