patches from David Goodger. Closes patch 101085.

patches from David Goodger.  Closes patch 101085.

* deletes cache
* adds firstweekday and setfirstweekday functions that allow user to control
  which day of the week is first when displaying calendars
* adds month, week, calendar functions that return their results instead of
  printing them
* adds symbolic constants MONDAY, ..., SUNDAY so users need not remember the
  ordinal values of the weekdays