BattlescapeGame: use perpetual alien-psi-weapon

	- instead of creating and deleting them on-the-fly.
UnitWalkBState: investigate why alien vs soldier sight-range seems uneven.
	- soldiers provoke reaction fire from aliens that are 1 tile further than
	a soldier's sight-range, obviating Mutual Surprise rule, when at distance.
	- postPathProcedures(), if CHARGING then getMeleeWeapon()
		- not mainHandWeapon
GraphsState: surface adj's.
BattleUnit: descriptions.
etc