Keep previous version on gitstable when releasing new version

[diderich]

Sometimes the release of a new version introduces new bugs. Sometimes they are specific to an installation and sometimes generic.

To make it easier to understand if an "issue" is a bug, it would be great if the previous version would be available on gitstable for some time (1 to 2 weeks after release) and the new release on gitdeveloper. This would allow to better identify issues by comparing the outcome on both systems (with identical data behind it).

[mariuszkrzaczkowski]

git stable is connected to github from the stable branch, it happens automatically