Support for or-logic during printing

[MenoData]

This is a vital feature especially for the French revolutionary calendar (see issue #615). For example:

The pattern "D MMMM' an 'Y|SSSS', an 'Y" does not yet support a sansculottides date (throwing an exception because such a date does not contain a day-of-month). The solution should analyze that the day-of-month is missing and then switch over to the next pattern part after the char "|".

Notes:

• For ISO-8601, this new feature is not relevant in most circumstances.
• Parsing is not affected (already well supported or-logic).