Content per directory

* doc
Currently this dir primaryly contains documentation on processors, but
AOS-documentation will be added.

* usbtest
An usb-loopback test written from scratch.

* src
The AOS-source

* oldstuff
Old unused and incomplete thing. 
- drivers     : A driver infrastructure inspired by Linux. 
- aostk       : AOS toolkit. Graphics framework.
- datastructs : Unused data-structures.