maxViewDistance, maxViewDistanceAtDark and maxDarknessToSeeUnits moved into ruleset.
TileEngine::visible() optimization.
Merge branch 'OpenXcomExtended' of https://github.com/Yankes/OpenXcom into view_distance_yankes

Conflicts:
	src/Battlescape/AlienBAIState.cpp
	src/Battlescape/TileEngine.cpp
	src/Ruleset/Armor.cpp
	src/Ruleset/Armor.h
	src/Ruleset/RuleItem.cpp
	src/Ruleset/RuleItem.h
	src/Ruleset/Ruleset.h
Merge branch 'view_distance_yankes' into OpenXcomExtended

Conflicts:
	src/Battlescape/AlienBAIState.cpp
	src/Ruleset/RuleItem.cpp
	src/Ruleset/RuleItem.h
Default values for night view range