v4 lives.   v4 introduces concrete subclasses of RealFilter.
Also bumped Jackson version.
Instance of vs Enum Switch, doesn't really matter.
V5
 - Type field used to differentiate sub-types.
 - Can support a List of type values like List<String>
 - Logical Filters now share getValues interface with real one, aka they return a List<QueryFilter>
V5
 - cleaned up and documented
 - Filled out top level Readme
more cleanup
Deprecated JsonUtil methods.
Additional cleanup.