[api] fix submit request with target to a package which exists in linked project. A package branch is executed before now.

Also note that Fräulein Configuration has left the building...

[api] * allow reviewers to add further reviewers

[webui] fix enabling of submit button after editing repositories. Don't crash afterwards, removing obsolete code by not allowing repo renames anymore and don't confuse by adding a repo instead of a path for now. (#617942)