AbiathRPC - Version check

I might eventually want to add some features to AbiathRPC after its first public release. Therefore, it'll need some sort of versioning system. I added an operation contract to the server's service contract that gets a string describing the server's version. If a client connects to a server with a different version, it warns the user about possible bizarre behavior. Since the client reports its own version when asking for the server's, the server has the opportunity to lie about its version if it decides it can accommodate the client despite their differences. That ability may or may not prove useful as I add more features after a release.