Bump tomcat version; fix slow apt; add org.label-schema LABELs; clean-up

- 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