Fix tile group validation functions

Fix tile group validation functions

	tile_group_is_set() has been tested
	and appears to be working. No major changes
	made here.

	tile_group_is_run_one() has been tested and
	appears to be working. This version has been
	significantly revamped. The concept for the previous
	version was "slick" but was flawed. One failure came
	from testing a 3 tile group containing a yellow tile.
	The yellow tile tried to increment index 3, but the max
	index was 2.

	no changes made to tile_group_is_run_two() which
	has not been tested. It may not be needed unless
	it can be shown to be "better" than _is_run_one()