Add a way of starting a server with the simulation paused

[rhoslynroebuck]

For the user study we would like to start the server before the simulation is actually needed. Can we add a way of pausing a simulation when starting a server? Then the simulation can be played only once the user needs it.

[jbarnoud]

Would that work for you:

• from the CLI, the --paused option causes the server to start paused
• from the GUI, a tick box "Start simulation paused" allows the same behaviour

In both cases, the simulation starts paused, and a client needs to run the "playback/play" command for the simulation actually to run.

[rhoslynroebuck]

yeah this sounds good.