Add some target platforms.

Summary:
  * Add many ARM docs.
  * Add some ARM platforms and drivers (arndale, smdkc210).
  * Split main.c-code to many files.
  * Start implement driver for ARM Generic Timer.

Need:
  * [Arndale] Done driver for ARM Generic Timer.
  * [Arndale] Tune GIC-400
  * [Arndale] Done context switch.
  * [RPI] Done work with MMU.