Put feature into own class, now can make other feature types that conform to having an img and x and y.  Need to make a getHeight function for each feature, also maybe a getFriction function later too.
Renamed wheels for clarity
Now getting height correctly for front and back wheels, though behavior of sticking to max height looks funny for pointy obstacles.
Now have reverse jumps, but the y position is off by 1.
I think I have the collision and bitmap placement set correctly.
Decent jump and gravity now.