TODO: Class variables should either be made private or made into properties

[relativityspace-jsmith]

Being honest, when I wrote this library originally, I did not really follow good practice with class variables. I made all the variables "public" (i.e. not starting with an underscore), so linters won't complain if other code uses then. And some of these class variables are used, especially the list of sockets (which is needed by users of multicast_expert who want to select multiple sockets at a time or set socket options).

What we need to do is make all the current class variables private, and then add property getters for any of the variables which external code has a legitimate reason to be using.

Note that this could end up being a non backwards compatible change which triggers a 2.0 release.