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
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
enforced node_update function with stronger checks
addressed issue https://github.com/globaleaks/GlobaLeaks/issues/614

* implemented permission check on postpone (minor vulnerability - was a clinet side check)
* implemented new error (Forbidden to extend date)
extended Tip unitTest with expiration date checks
solved https://github.com/globaleaks/GlobaLeaks/issues/612

* removed unused import in authentication.py
applied corrections to commit https://github.com/globaleaks/GLBackend/commit/9c3937d4cf9ce1172bdbe703cb991ed80cd9c719
Merge pull request #178 from globaleaks/issues/607_inverted_lists

reversed list of overview, files, tip list
Merge branch 'devel' into bugfix/614_comment_suppression

* devel:
  bump to version 2.27.1
  Added Czech translation
Merge branch 'devel' into bugfix/614_comment_suppression

* devel:
  applied corrections to commit https://github.com/globaleaks/GLBackend/commit/9c3937d4cf9ce1172bdbe703cb991ed80cd9c719
reversed list of overview, files, tip list