Improvements to movementV4
==========================
 tuning
    lpresent,rpresent,fpresent should be so low that the wall is always seen (if it is there)
	new values 
	#Used to determin what wall all present
	lpresent = 1100
	lnotpresent = 0
	fpresent = 1800
	rpresent = 1100
	fstop = 3300


lines 27,184,428
   gc.collect() is not needed (I think)

1 line 205
     forward() should adjust dist ONLY to reduce it, not to increase it
     forward() should adjust dist ONLY once.

2  line 277
      u_turn() should only do the go_back if there's a wall in front.

3  line 469
      the 'O' command calls go_back() not u_turn()
4  line 293
      u_Turn doesn't stop motors after spin.
   
4 line 457
Long straight run:
- a - it should go faster on the early cells and slow down for the last one
        the speed are called fast and slow Line 44.45.
- b - it should call forward once for each cell in the run, 
      not call a single time with a longer travel distance.
      This is because the forward() function corrects for cell length only once (or will do)
      and will reduce the distance to 1 cell at the first side wall change.
  line 458 still uses 28 as the fwd distance
  
Tuning
line 65  mult
line 21 set target in  maze_solver.Solver() constructor