Fix NRF51822 PWM and Serial:
- imlement pwmout_free()
- check UART interrupt type carefully
- implement serial_set_flow_control()
- add serial_clear() stub
[NUCLEO_F091RC] First commit of HAL files
[NUCLEO_F091RC] Update python files for this target, add uVision exporter
[NUCLEO_F091RC] First commit of CMSIS files
[DISC_F407VG & ARCH_MAX] change default toolchain
[NUCLEO_F091RC] pin_mode for Serial only if the pin is present

Same as all other targets.
[HAL][ARCH_MAX] use different PeripheralNames.h for STDIO_UART
[NUCLEO_F030R8] port HAL to support cube and ad cube files as well
[NUCLEO_F401RE] enhance gcc ld file