Ensure end = None if we cannot parse a date from it
If we cannot parse a date in the end parameter, then end is None

Thanks @puiterwijk
Merge pull request #129 from fedora-infra/filter_db

Filter db
Ensure that the end of the recursion is greater than the date of the meeting

Fixes https://fedorahosted.org/fedocal/ticket/124
Merge pull request #130 from fedora-infra/fix_ical

Ensure that the end of the recursion is greater than the date of the meeting
Increase unit-tests coverage for format_full_day_meeting
Small style change
Increase coverage of the delete_recursive_meeting by testing deleting a recursive meeting in the future
Check that the recursion re-starts after the single occurrence was deleted
Increase unit-test coverage for delete_recursive_meeting when deleting all the meetings of the recursion
Increase coverage of the edit_meeting by moving a recursive meeting in the future

And code style changes
Fix the fedocallib.update_date_rec_meeting method to work properly

* If the date_limit is earlier than the first occurrence of the meeting,
use the first date as date_limit.
* Check that the last_date of the meeting is greater than the first date
of the date of the meeting when returning the last occurrence
Add unit-tests for the fedocallib.update_date_rec_meeting method
Adjust the unit-tests for the list view