Add TARGET_STM32F3 folder with STM32Cube driver
Add NUCLEO_F302R8 specific files
Add NUCLEO_F334R8 specific files
Remove previous NUCLEO_F302R8 folder
Remove previous NUCLEO_F334R8 folder
Merge pull request #640 from bcostm/master

Targets: Factorisation of NUCLEO_F302R8 and F334R8 cmsis folders