installation-images got renamed
correctly expand the revision in rqlink
the ring projects are renamed

And we don't care for Rings higher than 1 atm
Nice titles for staging projects
remove the prosa from the staging title
simplify rqlink usage by offering osc staging select LETTER REQUESTS...
Extract StagingApi class from osc-staging
Update documentation about plugin installation
Integrate coolo's changes in StagingApi class