- Blocking and non-blocking behaviour is now very similar to TcpSocket's.
- IsBlocking(), IsWorking() methods are added.
- WhenDo replaced with WhenWait, and WaitStep() method is added

  Remove progress gate parameters in the getters and putters, and replace them with a single WhenProgress gate.
- Add WhenContent:   Consumer function for incoming data transfers.

  Change the Async (multithreaded) getters and putters:
- They will have progress gates with three-parameteres (id, done, total), instead of two. This proved more useful.
- They will use a URL similar to the one I use in the new version of FTP package.
- Additional variants for async functions, which will use One<Stream> and picks input data (for outgoing transfers). 


- Update libssh2, as it has seen some activitiy, and gained new ciphers.