Corrected rtc_hal function names
Added set rtc alarm function in rtc_hal and related updates
Move hardware specific stop mode code from spark_utilities to core_hal
Move standby mode code from hw_config & spark_utilities to core_hal
Move system specific Spark calls from spark_utilities to core_hal
Added HAL_Timer_SysTick_Handler in timer_hal and related timing changes
Rename to proper getter names for micros and millis in timer_hal
Add DFU_BUILD_ENABLE define in core_hal (normally defined via makefile)