Added a test for associative arrays.  All array functions should work with associative arrays because normal 'arrays' are associative, they just use numbers... there's no actual push/pop or integer counting for bounds.
Added support for getting keys and removing elements by key names from arrays.
Renamed array_Remove to array_RemoveKey.  This was an oversight.  I may create an array_RemoveValue down the road; either way this should remain disambiguous.