platform: add stm32-common to place stm32 specific code
platform: Move shareable gpio functions to stm32-common
platform: Move shareable rcc functions to stm32-common
platform: Move shareable mpu functions to stm32-common
platform: Move shareable nvic functions to stm32-common
platform: Move shareable systick function to stm32-common
platform: Move shareable hwtimer functions to stm32-common
platform: Move shareable usart functions to stm32-common
config: add platform selection in Kconfig
platform: Add stm32f429i platform support
mempool: Add AHB1 memory pool declaration
mempool: Add mempool declaration for stm32f429i
platform: Add LCD initialization functions for stm32f429i
platform: Add LCD utilization functions for stm32f429i
platform: Add stm32f429i lcd test case
platform: Add touch screen initialization functions for stm32f429i
config: Add platform default config for each board
travis: Travis now will check discoveryf4 and discoveryf429 build
Merge pull request #99 from slpbaby/stm32f429

platform: add STM32F429i Discovery support
README: mention STM32F429 Discovery Kit support