[generator] Use DateFormat and NumberFormat from icu4j

* Update FormatFactory and depending fields and constraints
* icu4j allows special financial rounding rules, e. g. for
  Switzerland

Change-Id: Ib2ae4dab9485433e3203652f3753c7e25daaea0e
Issue: 19
Merge "[generator] Use DateFormat and NumberFormat from icu4j"