Major upgrade

- Project files generated using STM32CubeF4 for both IAR and Keil
- Now using ST USB drivers instead of proprietary ones from Keil
- Now using FreeRTOS instead of Keil RTX
- Now using USB-MIDI class instead of USB-CDC
- Fixed a bug in Keil which caused an error in USB memory allocation
(heap too small, malloc failing to allocate buffers)