changed CustomUser model to contain new mail configuration
Merge branch 'develop' into feat-eventmailer

Conflicts:
	accounts/models.py
Merge remote-tracking branch 'origin/develop' into feat-eventmailer
aesthetical text improvement
bugfix
first effort in converting senddigestmails
only digestmail.html left to fix to have a first working version (but to be tested)
small changes to event_filters
broadened application of listeners_to_bundled_events
implemented mailer
small changes
added support for proposalLifecycleEvent
bugfixes
bugfixes
first version of test
fixed bug
first fully working test
bugfix
finalized test.py
refactored senddigestmails