All #ifndef guards on headers have been removed, I think,
in favor of #pragma once
Headers are now included as `#include "filename"` if the included file
resides in the same directory as the file including it, or any
subdirectory therein. Otherwise they are included as
`#include <project/top/dir/relative/path/filename>`
The above does not include system/os headers.
* bump zmq static dep
* lokimq -> oxenmq
* llarp_nodedb -> llarp::NodeDB
* remove all crufty api parts of NodeDB
* make NodeDB rc selection api not suck
* make path builder api not suck
* propagate all above changes so that unit tests work and it all compiles
