cleanup: do not use TileConstants. prefix when not needed
api: getTile() now returns masked tile number

use getTileRaw() to get the raw tile number
api: TileConstants- never accept "raw" tile numbers
api: use clean tile number for isZoneCenter
api: another use clean tile number for isZoneCenter
cleanup: use named constants in isRiverEdge

instead of hard-coded numbers
api: use clean tile number for isCombustible
api: another use clean tile number for isCombustible
api: use clean tile number for isConductive, isOverWater, etc