Separating openvpn3 lib and bin

[IamtheMZI]

If we need to use just the ovpnclil library we can just use the ovpncliwrapper without the need to understand the library code.

[schwabe]

I am not sure what the goal here is. cli.cpp is just a demo/test client that shows how to use the openvpn3 library. I don't get the benefit of moving its main method into a different file. You need to explain the problem you are trying to solve here more.