fixed mock hardware for botwheel explorer

[ErikParkerrr]

Goes along with this issue: https://github.com/odriverobotics/ros_odrive/issues/24

Pretty much everything was already setup in the official repo. The only thing missing was the command and state interfaces for the mock_components/GenericSystem plugin to recognize. I've assumed adding these will not break anything for the non-mock-hardware usage. If it will, it can be changed to be in an if statement.

Cheers