Puzzles fixes

karel_2_10
- there's a valid solve where you never check for a hole that should be allowed

turtle 1_4, 2_1, 4_1
- these are all levels in which if you go through the path backwards rather than forwards, we were claiming non-success.  With these changes, our feedback reporting will be the same (i.e. we will tell you to use the move forward/go right blocks), but we will also allow a solution that uses left/backwards blocks.

turtle 2_3
- I made some changes to turnRight to get it to look the same as turnLeft.  I noticed a bug in my initial change that wasn't getting caught by any of the level tests, so I added this test to make sure that code gets exercised.