contrib/docker/ubuntu.template

hook: give exthooks tags for blocking time

The ui.system autogenerated tag isn't really useful - as they're named, let's
use the name the user gave us.

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