Groundwork for feed override handling
Tried constant acceleration from previous step, but this tends to overshoot
Assuming zero acceleration is a bit smoother, though not the perfect answer. it also has the nasty side-effect of not quite stopping at the end of the straight segment test.
Forcing the last desired velocity to finalvel has the same effect as nothing at all on the arc test
Removed islast from TC_STRUCT since it's not needed anymore
Refactored optimization function
reduced optimization's speed step by 1/2 to combat overspeed due to overshoot