Drive motors configuration

[sssemil]

This PR allows configuring the drive motors' stop position entirely in software. I made this, since I cannot easily configure my drive motors, because they are just patched servos.

[0xD0M1M0]

I like the PR. The code looks good, testing is pending time for integration.

In the "config_drive_motor_neutral.py", I would leave the people a choice if they have motors with potentiometer and guide them with the old instructions trough the settings, while on others the proposed way seems appropriate. I also would leave the sample values and mark them clearly as calculation sample or even propose a small script to calculate the the neutral value as starting point based on the specifications of the motors (if known).