Release 0.2.0

From https://open.greenhost.net/openappstack/openappstack/issues/207:

Release checklist:

• update/review documentation and make sure it matches the current state
  • Update how to checkout the latest stable tag
• update CHANGELOG.md
  • Include Known issues
• update the version number in the VERSION file
• commit
• create signed tag (git tag -s 0.2.0 -m'Release 0.2.0')
• Push to MR, including tag