SSH package for U++
--------------------
SSH package is a feautre-rich, flexible yet very easy to use libssh2 wrapper for Ultimate++.
It supports both console and GUI-based applications on POSIX-compliant operating systems and
MS Windows (tm).

Currently it is in beta (version 1) stage.

Classes:
--------------------

- Base (core) class  -> Ssh
  - Ssh session        -----> SshSession
  - Sftp subsystem     -----> SFtp
  - Ssh channel        -----> SshChannel
      - Scp channel                 -----> Scp
      - Exec channel                -----> SshExec
      - Real-time interactive shell -----> SshShell
      - X11 forwarding              -----> SshShell (as operation mode)      
      - Tcp/IP and port forwarding  -----> SshTunnel

- Known hosts manager -> SshHosts

Features and Highlights:
--------------------

- Ssh-derived classes have pick semantics, based on RAII principle, support RTTI, and allow
  polymorphism (i.e. different classes can be stored in the same arrays, etc.) through a common
  interface. 
- Uses U++ memory allocators (Native allocators is also a compile-time option)
- Uses OpenSSL by default. 
- Supports time-constrained, blocking and non-blocking operation modes.
- Supoorts multithreaded file transfers and remote command execution (exec), using worker threads.
- Supports 3rd-party network proxies. (Such as NetProxy)
- Supports known hosts verification mechanism.
- Supports password, public key, host-based, and keyboard-interactive authentication methods.
- Supports ssh-agents.
- Supports real-time interactive command line (shell) interface with both console and GUI integration (works on Windows and Posix-compliant OS'es)
- Supports multiple X11 connection forwarding.
- Supports Tcp/IP and port forwarding.
- Supports detailed (full) debug logging.

Todo:
--------------------
- Add more high level methods.
- Refactor Ssh (core) class.
- Improve documentation.

Reference examples:
-------------------

- SFtpGet:           Demonstrates basic SFtp file download in blocking mode.
- SFtpGetNB:         Demonstrates basic SFtp file download in non-blocking mode.
- SFtpGetMT:         Demonstrates basic SFtp file download, using a worker thread.
- SFtpGUI:           Demonstrates a basic SFtp browser with GUI (with upload, download, mkdir, rename, delete commands).
- SFtpMultiGetMT:    Demonstrates SFtp dir listing and concurrent file transfers, using worker threads.
- SFtpConsumerGet:   Demonstrates the usage of a consumer function for SFtp download in blocking mode.
- SFtpConsumerGetMT: Demonstrates the usage of a consumer function for SFtp download, using a worker thread.
- SshExec:           Demonstrates basic Ssh remote command execution in blocking mode.
- SshExecNB:         Demonstrates basic Ssh remote command execution in non-blocking mode.
- SshExecMT:         Demonstrates basic Ssh remote command execution, using a worker thread.
- SshKeyboardAuth:   Demonstrates basic Ssh interactive (challenge-response) authentication method in blocking mode.
- SshLoggingExample: Demonstrates the logging capabilities of SSH package.
- SshOverTor:        Demonstrates a basic Ssh connection over TOR, using a third-party network proxy adapter.
- SshPolymorphismNB: Demonstrates the polymorphism capability of SSH channels in non-blocking mode.
- SshShell:          Demonstrates a basic, real-time SSH shell console in blocking mode.
- SshShellNB:        Demonstrates a basic, real-time SSH shell console in non-blocking mode.    
- SshShellX11:       Demonstrates a basic, real-time SSH shell console with multiple X11 forwarding.
- SshShellGUI:       Demonstrates the basic GUI integration of SshShell class with multiple X11 forwarding, in non-blocking mode.
- SshTunnelExample:  Demonstrates the basic SSH tunneling (as tunnel/server) in blocking mode.