Add DFU programmer for STM32. 

ToDo: 
 - Unify with dfu-programmer.py
 - Test with other STMs (adopt VID:PID)
Use stm32f3_discovery.hpp instead of manual typedefs.
[quickfix] Activate CAN1 on STM32 F3.
Add example for STM32 F3. Tested.
Merge branch 'develop' of github.com:roboterclubaachen/xpcc into develop