Merge pull request #2065 from FinalAngel/feature/fixes

Visual Debug Information
Fix broken tests:

since MLNGPlaceholderActions.de_copy_languages doesn't enforce order on the returned languages,
comparing lists in tests might give false positives
=> we need to assert sets are equal
Merge pull request #2086 from FinalAngel/feature/fixes

Frontend performance improvements
Merge pull request #2087 from yakky/feature/set_copy_languages

Fix broken tests:
make runtests-isolated.py Python 3 ready
made runtests-isolated.py better
Merge pull request #2099 from ojii/better-runtests-isolated

made runtests-isolated.py better
Merge pull request #2090 from FinalAngel/feature/fixes

adds additional features and ui improvements