[platforms] reorder platform/Kconfig to better map features and chipsets
[stm32f4discovery] skeleton for stm32f4 support - copied from stm32f3. doesn't compile
[stm32f4discovery] platform consts
[stm32f4discovery] correct makefile
[stm32f4discovery] better header of system_stm32f4xx.c file
[stm32f4discovery] linker script fixes - correct flash & ram sizes and sections
[stm32f4discovery] better comments on ISR placements
[stm32f4discovery] change misc.c file name, add CPU type define
[stm32f4discovery] adaptations - correct resource defines, remove GPIOs for now