Add new Fragment tool params to central processor

Many thanks to audioglider for this excellent Fragment tool update.  PD
now offers the same breadth of features as Paint.NET's Fragment tool -
very cool, and an elegant implementation as well!

@audioglider - what do you think of this slightly modified bounds
checking procedure?  IMO, restricting only the out-of-bound variable
(just x or y, instead of both) helps reduce banding at edges when the
distance parameter is large...?