Add automatic email remainders for workouts, refs #48

--HG--
extra : amend_source : 89b81cb70712bd578456a5d59826336ec29a2fec
Add simple test case to check the end date for a schedule
Testsuite for the email reminder command

--HG--
rename : wger/manager/management/commands/email-remainders.py => wger/manager/management/commands/email-reminders.py
extra : amend_source : 7d7148db9797aa8a87337923384892a6e2779175
Add notification language option in the user profile and tests

This is needed to allow for the user to receive notification emails
in a language of his choice since this information is not available
e.g. when running scrips via cron or similar where there is no request.
Add iCal export for workouts
Add test for iCal export for workouts
Also export schedules as calendar files
Add last date the user was notified about expiring workouts

This is needed e.g. to check daily per cron for old workouts but only
send users an email once per week
Don't check for expiring workouts if user has provided no email
Update django version to test
Merge