Add the arch/big picture omnigraffle diagram

To avoid losing this diagram again let's keep
it in the source tree so that others can modify
it and extend it as they desire (and also prevents
it from disappearing).

Will need omnigraffle to view:

https://www.omnigroup.com/omnigraffle

Change-Id: I44eb15722c9d6f2c63d965ff8f849efbdf15bbfb
Merge "Add the arch/big picture omnigraffle diagram"