SSH Tunnel support

[ppvan]

TODO:

• [x] Add libssh2 to project
• [x] Implement simple password ssh auth
• [ ] Implement public key auth
• [x] Working POC, can handle simple query
• [x] Robust buffer handling
• [x] Handler query cancel
• [ ] Error handling
• [ ] Testing service
• [ ] Design UI
• [ ] Implement UI
• [ ] Intergrate with service