-- addition of varaible region size in X and Y
-- internal storage of heightmap changed from double[] to short[]
-- helper routines for handling internal structure while keeping existing API
-- to and from XML that adds region size information (for downward compatibility,
output in the legacy XML format if X and Y are 256)
Updated and commented Constants.RegionSize but didn't change the name for compatibility.
to denote terrain format revision.
Add terrain DB format revision codes to ISimulationDataStore.cs.
Setup so legacy compatible terrain storage and fetch is possible while
allowing future format extensions.