Use the livenessProbe of `dsapce-deployment.yaml` to check
- tomcat response
- postgres reachable
- cron-hack from `dockerfiles/commul-customization/entrypoint.sh` either
  running or waiting

Fix #60 (again...)

Address #60

Address #60

Address #60

See, for example, https://github.com/moby/moby/issues/18017; ARG may
invalidate following `RUN` statements because it implicitly alters the
build context.

Also, use
* apt.local.conf
* ubuntu-16.04.sources.list

Fix #64

- add org.label-schema LABELs for version, build-date, vcs-url

- use latest 8.0 tomcat version (=8.0.53)
- build and install Apache Tomcat Native Library
- use mirror://mirros.ubuntu.com URL schema in apt.sources to speed up
  downloads
- add org.label-schema LABELs for version, build-date, vcs-url
- reduce multiple apt-get update/install invocations