cleanup_projects missing

[goofy79]

Hello,
i think a "nice to have" feature was, if you have a function
like ./elbe control cleanup_all_projects and/or ./elbe control cleanup_failed_projects

for example, you have an error in on self-made paket you get a long list of failed projects
and this need a lot of diskspace.

[bgermann]

Another possible improvement that would address this problem space: Introduce a elbe submit flag --force-removal.