OBMFULL-4633 Mandate a default time format in Of_Date.

Prevents PHP from complaining about lookups with non-existing keys.
OBMFULL-4633 Adds a method to count the number of days in the month.
OBMFULL-4633 Method to get ISO week day in Of_Date.
OBMFULL-4633 Adds a class to compute recurrence instances.
OBMFULL-4633 Adds getRealRRule() to get the original RRULE.
OBMFULL-4633 Computes the end of a recurrent event more faithfully.