Allow for disabling of shifting using hall effects.

There is a new constant that, if set to true, will make it simply
set the shifter pistons and not try to velocity match. This is
for the third robot, in which the analog hall effect sensors on
the shifters may never end up working correctly.

Change-Id: I344e4cf9fcca4fd32347da56d8b48e8a9fd5332e
3 files changed