1. Remove assumption of style from
  2. Copy existing Filter Implementations, and remove AbstractFilter superclass
  3. Package up as a FilterFactoryImpl
  4. Use a hint to try out existing test cases with FilterFactoryImpl
  5. When encountering geotools FilterVisitor; rewrite as a geoapi FilterVisitor (use DuplicatingFilterVisitor as an example)
  6. When encoutering a geotools Filter or Expression follow the update instructions to search and replace the OpenGIS counterpart
  7. Move org.geotools.filter interfaces to "legacy" module