Add Wizard.OpenLeftTitleNextBackDialog (bnc#868859)
version + changelog
Merge branch 'master' into title-left-api
Merge pull request #216 from yast/title-left-api

Enable wizard title on the left instead of on top during the installation (bnc#868859).
Refactoring: Parsing files moved to separate functions
Prefer os-release file to content file

- content file is usually broken and should be only used as a fallback
- there is no content file on a running system and thus returns different
  results comparing to the installation
- this unifies the running system with installation
new changes file entry and new version