Pathfinding: allow various parts to provide BIGWALL_BLOCK

GeoscapeState: remove weekday from sidepanel
	- put day/month/year into a single date string
Globe: change color of baseLabels
GraphsState: force aLienActivity to blink in unison.
BattleUnit: give chance of Reaction increase from Firing experience

force transparent color index on AlienInventory sprites
force transparent color index on FontBig