[IMyoDeviceBridge API Break] MyoDeviceDriver Can Throw Descriptive Myo Exceptions

- If you implement IMyoDeviceBridge, the method signatures have been changed to return MyoResult enum values.
- Changed here are made possible by previous commits that extracted Myo-specific exception creation.
- Modified the MyoDeviceDriver implementation to throw descriptive Myo exceptions.
- Added unit tests for the MyoDeviceDriver class.
- The hub class introduced a small amount of tech debt to avoid API breaks. I figured it was more likely someone made their own hub implementation instead of their own IMyoDeviceBridge implementation, so I chose to try and maintain compatibility here.

Author: ncosentino