Limit series

When adding a series, the calendar now adds a lot of entries (two years, I think). This means that making small changes takes quite a long time
Perhaps we should either:

• Limit the duration of a series to 1 year instead of 2 years

• Make it adjustable how long we want the series to repeat (for x number of days/weeks/months/sessions)

Or, of course, we could do both :)