Adding initial Teensy 3 support, compiles, but not fully functional yet.

- CDC Output seems to be working
- USB Keyboard output has not been tested, but is "ready"
- UART and Timers have not been tested, or fully utilized
- Issues using Timer 0
- Initial template for MBC-55X Scan module (only module currently compatible with the arm build)
- Updated the interface to the AVR usb module for symmetry with the ARM usb module
- Much gutting was done to the Teensy 3 usb keyboard module, though not in an ideal state yet

USB/pjrc/arm/usb_keyboard.h

@@ -0,0 +1,10 @@
+#ifndef USBkeyboard_h_
+#define USBkeyboard_h_
+
+#include <inttypes.h>
+#include "usb_com.h"
+
+uint8_t usb_keyboard_send(void);
+
+#endif // USBkeyboard_h_
+