The first PR for properties has just been merged (#479). Here's roughly what's left to do, one PR per item:

• (PR [core] Properties refactoring: factorized enumerated property #518) Work on enumerated properties:
  • Modularise EnumeratedProperty and EnumeratedMultiProperty like what's been done for eg NumericProperties. That allows both properties to share behaviour even though they're not related inheritance-wise.
  • Make a new constructor for enumerated properties with the same signature as before (without the Class<E> parameter) for retro compatibility, but deprecate it
• (PR [core] Properties refactoring: Move static constants of ValueParser to class ValueParserConstants #587) Move the static constants of ValueParser into a new ValueParsers class.
• (PR [core] Moved properties to n.s.pmd.properties #620) Move all property-related classes and interfaces into n.s.pmd.properties (see this)
• (PR [core] Builder pattern for properties #669) Replace the factories for properties with a Builder pattern (see this and this)
• (PR [doc] Update the documentation for properties #749) Update/Create documentation about rule properties. See this for the existing docu...
• Update the changelog - document API changes

We also need to complete the documentation and update the tests for good coverage. Feel free to add your ideas!