improve collection handling, esp. non-cumulative mapping

Currently non-cumulative mapping replaces the existing
object with a new one, mapping the existing one to the
new one. This drives e.g. Hibernate crazy,
necessitating a merge() operation, and will most often
blow away changes the destination object was intended
to receive as part of the mapping operation in the
first place. The attached patch will correct this
error for set, list, and array handling. Additionally
it removes the superfluous mapSetToSet() method (the
logic for mapping any collection to a Set is superior,
including non-cumulative support) and adds
non-cumulative support when mapping maps to maps (using
key AND value equality). Patch created against Dozer
21XBranch.