[FEATURE] Named weeks

[wake42]

Is your feature request related to a problem? Please describe.
I'm trying to model the Glorantha calendar, see http://www.backtobalazar.com/gloranthan-calendar-editable-file/ and there the week names are important since you write dates like <Month name (season)> / <week name> / <day of week>
For example Earth season / Truth week / Clayday or in shortform earth / truth / clay

Describe the solution you'd like
To model this it would be great if one could name weeks, similarily to how years can be named. For the Glorantha calendar the names should repeat each month (season), but to be general I guess there should be an option to repeat on year also. The Glorantha calendar also has a month that doesn't follow the rules - Sacred time - that only has two weeks which are named differently. Perhaps this could be modeled as intercalary month with special rules?

In addition there should be an option to show a short form of the week name to the left of the week in the calendar view.

Describe alternatives you've considered
For now I've modeled it so that each week is a month.

Additional context
To make this work this issue #137 is also needed so that one can customise the date representation