Allow note on/off. Use SoundEffectInstance instead of SoundEffect. Allow regular number keys also..
Significant update of Arduino code:

- Added calibration code to calibrate the thresholds for the detectors by powering the lasers on and off and monitoring the photoresistors.
- Change the protocol to single byte for each change: "A"  - 'H" for laser interrupted, "a"-"h" for laser back on.
Updated serial monitoring code:

- Use new serial protocol to match Arduino
- Show Windows Form which we can use for some UI (just blank for now)
- Regular digit keys work as well as numpad keys
- Test using the pitch modification on SoundEffectInstance.
Several bug fixes for Arduino.