Move <fields> to top level of <dates> element

Deleted Component: xxx-dtd

Per TC discussion 2012-Dec-12: Move the <fields> element from its current location -

under <dates><calendars><calendar type="xxxx"> (with data only for "gregorian") -

to being directly under <dates>, and applicable to all calendars.

Involves change to DTD, data, LDMLConverter, and coordination with JDK.