Fix some of the constants in drivetrain.

This includes the shifter hall effect constants, for which
I guessed whether we were using the drivebase from the old comp
or practice bot, and guessed wrong. They also include the
drivetrain python code, for which some of the constants weren't
correct.

(This was formerly a part of I3d012fb8a9652c0b85ed27f5d23fe7d63bb977ce.)

Change-Id: I5869b7e57a039131018150c690287f81670a3483
4 files changed