The global TranslationCleanupJob should be configurable per project

[cbaoth]

The TranslationCleanupJob seems to remove obsolete keys + translations, those that are no longer available within the leading language file.

The problem here is, that this job performs the cleanup on all projects at once. There doesn't seem to be a way to configure this on a per-project basis. If you have many projects you want that each project admin can decide whether he wants to activate this cleanup mechanism for his project or not.

One simple solution could be, that projects get a "cleanup" flag so that the job only performs his cleanup action for those projects that have the "cleanup" flag set.