PersistentMap interface
Remove update functions (MapUpdate and SetUpdate): no use case.
interface MutableMap extends Map for efficient bulk updates
Add missing copyrights
Call Merger.merge() also when re-associating entry
Preparation for PersistentSortedMap interface
interface for PersistentSortedMap - not implemented yet
Red Black Tree Maps implement PersistentMap and MutableMap
Common base class for PersistentMap tests. Improve test coverage.
Improve RBTree tests and fix delete.