Moved sf and serial_tun to tools

I have no idea if anyone still uses this code. The configure script for
sf is out of date and does not work with newer automake (I updated it).

I also renamed some binaries so they can be installed. If the user is
installing TinyOS, they may as well _install_ tinyos. Why make them hunt
around for different binaries? If something shouldn't be installed, then
the question is why is it distributed with the main TinyOS source? It
should be some sort of optional extra somewhere, not part of the main
source. Hard drives are big, just give me all of the TinyOS tools.