Some maintenance in PosixMain.cpp

Stephen, does this all look OK?

Functionality changes:
* Restore --uuid option, prints out hostname:port
* -H can now be used as a short form of --add-host

Bugfixes:
* Don't log anything before loggers are initialized
* Don't log anything when using -v, -u, or -l

Misc:
* Add generate_uuid function to unnamed namespace
  (removes a slight bit of code duplication)