Initial push for NNN NULL packet

This is the initial compiling push of the NNN NULL packet.
NULL packet license

Got too happy pushing the packet and forgot to change the license.
Graph font size

The graphs produced by the scripts are hard to see on the screen. It was
unfortunate that I had to do a presentation to find out.
More silly issues with nnn-nullp.h

Forgot to delete some variables that would not be used in the new NULL packets.
NULL packet doesn't need NNN address

Another small annoying change. The NULL packet doesn't need the NNN address
information.
More errors in NULL packet header

Length should be an unsigned integer. This patch fixes this mix up.
Error in comments for NULL packet

More small changes.
The small errors continue to annoy NULL packet

Unsigned integer function signature in NULL packet implementation.
NULL packet implementation changing constructors
Initial commit for NNN SO and DO packets

This is the initial naive implementation for SO and DO packets
DO packet implementation was missing

Added in this patch
Added a new append function to nnn-address.h

Used when sending stuff through the wire. It was easier to implement than to
change the existing code.
Huge update from Zhu

This adds the files given to me by Zhu. There have been some modifications to
make the code compile. Most of it is to make it easier to read.

The nnnsim.cc file is empty and must be filled in as the serialization
process is still not clear to me.

The NNN Address serialization must also be checked as I basically copied it
from the NDN code.

There is a lot of confusion in the wire models and I will have to see if
making a few folders wouldn't make the whole repository a little cleaner.

For today this is enough.