remove diagonal handling for doors.
slight alteration to getTUCost to better handle stairs.
modify bigwall flag to integer

this will help us better define how to behave around certain "bigwall"
objects we encounter while pathfinding.
removes the hack for landing craft walls.
implement ruleset-based MCD patches

while this class does require expansion to accommodate everything that
defines a mapData object, it does provide a "good start" that should be easy
to copypaste all the rest later on. for now i'm just adding in some bigWall
integers to differenciate them a bit, for the improvements to the
pathfinder.