Added a handful of useful coordinate getters for Tile.
Flipped operands of '||'. Probably more optimal.
Cleaned up OKMoveDest method with getTilesOnLine().
Moved isAnOkMoveDest distance check.
Added argument validation to canBeSeenFrom(x,y,range).
Wrote distance check properly.
Deleted some obsolete lines.
Added argument validation to getTileAt methods.
Added argument validation to getTilesOnLine().
Cleaned up some leftover imports.