Handle sensor failures

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Make sure that if an encoder stops working teleop, the robot gracefully switches to open loop control. This should be something that works for the lift and the drive. Open loop lift might be tricky, but you should be able to figure it out.

See 2017 code for details: https://github.com/CRRobotics/2017Robot/blob/master/src/Commands/Drive/JoystickDrive.cpp

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Wait, it looks like this is handled already. Is this implemented for acquisition though? Also make sure all these failure modes have been tested by actually enabling the robot and then unplugging the encoders.