Finalise converting the delegate method

Now that the dispatch is handled in the property class, it can
be non-virtual, and completely removes the need for a lookup to get the
property instance.
Update the BiomassProperty as a delegate
Write about my failings.
Update BurnSpeed and Teleport properties to use delegate
Convert TerrainModProperty to delegates
Remove last test use of active properties
Remove unused HandlerProperty
Remove obsolete HandlerProperty include
Remove obsolete handlerProperty