Rename of files, improved for handling, add cb hints

- Rename Test to Ink as main file
- Support more errors for for loops.
- Add hints to cbs

test/for_no_iter.ink

@@ -1,6 +1,6 @@
 vertex main :: () {
 	x := 0.0;
-	for i : {
+	for i : 0.. {
 		x += 2.0;
 	}
 }