Implement toEpochDay
implement plus.
Switch to multiplying in plus(...) method.
Add minusXxx methods.
Implement until(...) and sub-methods
Implement until(ChronoLocalDate)
Correct getProplepticMonth().  Leap years were moving the count in the
wrong direction.
Add todo reminder.
Remove comment, inherit from interface.
Implement with(...) and submethods.
Add minusWeeks.
Implement plusDays
Add comments for plusWeeks