Main functionality, returns path from self to dest

Property definitions

a_star $ Node :: path_to
	# Main functionality, returns path from `self` to `dest`
	fun path_to(dest: N, max_cost: Int, context: PathContext): nullable AStarPath[N]
	do
		return path_to_alts(dest, max_cost, context, null)
	end
lib/a_star/a_star.nit:93,2--97,4