Interface the drivetrain class

[Lock-The-Door]

The drivetrain code constantly freaking out is really concerning.

To prepare in advance, we should create a drivetrain interface with the same existing functions already implemented so we can easily swap out of the okapi lib if we need to.

As of writing this, the only important part of the class is the drive function which takes in two controller values to implement arcade drive and a getVelocity function which returns the current velocity.