No Support for JapaneseChronology before Meiji 6

The Japanese calendar before Meiji 6 is complex and has multiple interpretations. Until there is agreement on the calendar before then, the JapaneseChronology should throw an exception for dates before Meiji 6 Jan 1. The start of Era should be set to the year-of-Era and day-of-year is correct starting in Meiji 6 (jan 1) but earier dates are not valid.

Supplemental information:

The existing dates from java.util.Calendar for the Japanese calendar are not correct. 1968-01-01 is to extend Gregorian backwards from Meiji 6 in which Gregorian was adopted in Japan. This is because of the lack of the Tenpo calendar (a lunisolar calendar) support. 1868-01-01 is wrong, but intentional in the sun.util.calendar implementation.

09-08 is the Keio-Meiji transition date in the lunisolar calendar, which doesn't make sense in Gregorian. Its real Gregorian date is 1868-10-23. Note that the whole lunisolar year became Meiji 1 by the era transition rule at that time. The real Meiji 1-01-01 is Gregorian 1868-01-25. If JSR 310 needs correct Meiji support before Meiji 6, the lunisolar calendar must be supported.

Also see Github issue #326 https://github.com/ThreeTen/threeten/issues/326