[STM32F0] Add TARGET_STM32F0 folder

With STM32Cube inside.
[NUCLEO_F030R8] Move files in STM32F0 folder
[NUCLEO_F072RB] Move files in STM32F0 folder
[NUCLEO_F091RC] Move files in STM32F0 folder
[NUCLEO_F030R8] Remove old folder
[NUCLEO_F072RB] Remove old folder
[NUCLEO_F091RC] Remove old folder