Add devops workflow for containers and release zip files

[Heiss]

TODO:

• [x] workflow only executes, when a tag v* (e.g. v1.0, v0.2) was created
• [x] build all needed packages
• [x] zip all dist folders and server files
• [x] create and push docker containers
• [x] create a release on github
  • [x] add zip files
• [x] add docker-compose for easy setup
  • one to setup owncloud easily is already here
  • now, we need one or add this to existing one with RDS-Web
• [ ] use this setup for demo instance sciebords.uni-muenster.de
  • [x] set up oc-web there
• [x] javascript needs something to reuse env vars from docker container
  • current approach: replace $ENVVAR strings in code... ugly but works
  • be aware: process.env should be valided too.
• [x] fix l10n