Feature/date time mstimer clock (#861)

* Added daylight savings time calculation module with unit testing.

* Added datetime daylight savings time and clock API

* Added basic datetime_local() clock using mstimer as basis and time-sync option.  Integrated clock with ports/stm32f4xx example.

test/CMakeLists.txt

@@ -171,6 +171,7 @@ list(APPEND testdirs
   # basic/sys
   bacnet/basic/sys/color_rgb
   bacnet/basic/sys/days
+  bacnet/basic/sys/dst
   bacnet/basic/sys/lighting_command
   bacnet/basic/sys/fifo
   bacnet/basic/sys/filename