Fix #314: add ssh+tmux wrapper scripts

The `concert-server` script starts a new tmux session concert-PID and starts a
concert session with arguments passed to the start command. The
`concert-connect` script connects via ssh to a remote machine where such a tmux
session must be running and attaches itself to it.
Don't disaply empty windows on ctrl-c by pyplot
ufo: separate stopping input tasks from waiting
Don't manipulate future results in resolve
Make PyplotViewer work nicely with resolve
Add Range for holding quantities and their ranges
Make scan multidimensional
Test multidimensional scan
Update the docs for new scan