beagleOS: Write a simple OS for BeagleBoard

#----v0.0.2
Rewrote the hellow world printing code with ARM assembly.
Makefile was modified to build the u-boot.bin from startup.S , instead of startup.c 

#----v0.0.1
Print hello world into console
The result is u-boot.bin , need to copy into a sd card or simulator img file with MLO