Add enable-sftp option, init/free SFTP as needed.
Initial stab at SFTP file upload.
Move SFTP to own SSH session - does not work when combined with terminal session.
Fix permissions of upload.
Validate filenames.
Stub out guac OSC handling.
Move SFTP functions to own file. Stub out download function.
Add initial guacctl implementation.
Add stub ack handler. Call SFTP functions when download code received.
Track number of active pool integers. Track output streams.
Implement file download.
Resolve full path in guacctl.
Add license block to guacctl.
Implement directory set.
Finish functionality+docs for guacctl. Add guacget symbolic link.