Add event recurrence function

[izhanchang]

There could be an option to have an event repeat weekly/monthly that copied the info from the first occurrence instead of entering separate but near identical events in a row. Each individual occurrence would still be editable and able to be deleted as needed. Thinking specifically of weekly meetings and Tartan Tailgate events that don’t change too often.

[DaAwesomeP]

Could be partially help by #411