Remove deprecated proxy connect methods from SocketClient

[exceptionfactory]

This pull request removes deprecated connect() methods from SocketClient that support connections through a proxy server. As described in comments, proxy support can be implemented using a custom implementation of the standard Java SocketFactory.

The deprecated method comments indicated that these methods would be removed after version 0.12.0. Removing these deprecated methods provided the opportunity to remove the custom Jdk7HttpProxySocket class and the associated JavaVersion class.

[hierynomus]

Actually not entirely correct, we still support Java7 for the rare enterprise case, so even for a SocketFactory you would need the custom Jdk7HttpProxySocket.

[exceptionfactory]

Thanks for the feedback @hierynomus! What do you think about removing the connect methods, but retaining the Jdk7HttpProxySocket class?

[exceptionfactory]

@hierynomus, following up on this, do you want to remove the deprecated connect() methods that accept Proxy parameters? If not, I can close this pull request.

[hierynomus]

Yes, was about to merge this one actually ;)

[exceptionfactory]

Sounds good, thanks!