https://github.com/billchurch/WebSSH2/issues/112
This commit send 'reauth' command to the client, when err.level === 'client-authentication'.
The client itself binds the 'reauthSession' function to that command, so it will automatically request authentication, every time the authentication fails.
The client bundle (webpack) is also rebuild with the made changes.
Move bulk of server .js file files to /server, all client related files
live in /client (including /public), webpack scripts now live in
/scripts, cleanup of paths in /client/src/js/index.js and webpack.js.
