The changes to support multiple Hijrah calendar variants resulting
in significant changes to the implementation of HijrahChronology, HijrahDate,
and related classes.

The variants are identified by new properties in lib/calendars.properties.
Each variant is defined by a properties file containing id, type, hijrah start and
corresponding Gregorian start dates plus month lengths for every month.
The format and contents of the properties file is still being reviewed.

Please review and comment:

javadoc:  (only the Hijrah classes are updated)

The related issues are:
  # 95 Deviation Options for the Hijrah Calendar
  #118 Confirm calendar system type of Islamic

Thanks, Roger