rework Network send() code to use NetworkTarget/Node/Group::send classes, add a NetworkMessage class for sending NetworkObject messages, and fix a bug whereby the server's client TCP sockets weren't nonblocking.... I wonder how this has worked before?\!

/* This file is re-generated on each build */
const char *PROJECT_VERSION = "@PROJECT_VERSION@";
const char *PROJECT_BUILD_TIMESTAMP = "@PROJECT_BUILD_TIMESTAMP@";