Revert the addition of BLIP_NO_RADIO

pound defines are ugly, and adding one for not using a radio in blip,
which is designed for doing wireless ip, is nonsensical. Therefore, I
removed it and added dummy files in the CoapPpp application that has the
same effect but doesn't munge up code for the sake of a single
application.
Blip cleanup

While looking over some details of blip I noticed that it could use a
cleanup pass. Mostly I added comments and reorganized component wiring.
I also deleted unused code and interfaces that were not wired to
anything in tinyos-main.

I did not change any functionality of BLIP.
cc2420xDriverLayer: remove bogus comment

there was a comment about turning on the SFD capture interrupt when turning the Radio OFF.   This makes no sense.   nuke it.
Drop IRQs while the radio is turning off. Fixes #236, submitted by @ucolesanti