enhanced unitTest in notification
Add some code useful for debugging memory leaks and such

You just do a killall -3 python and BOOM, you got some pdb.
restored log functionality, removed by mistake, enhanced log exception report
Merge branch 'issues/notification_update_566' into bugfix/612_notification
solved conflict, tested patch, fixed issue https://github.com/globaleaks/GlobaLeaks/issues/613
fixed wrong keyword in Comment default notification template
reversed list of overview, files, tip list
fix against https://github.com/globaleaks/GlobaLeaks/issues/611
added also store.invalidate to finally kill the memory leak
Merge branch 'issues/607_inverted_lists' into devel
Merge remote-tracking branch 'origin/fix/memory_leak_2' into devel
Merge branch 'bugfix/612_notification' into devel
Merge branch 'feature/memory_leak_debug' into devel