Honor "when" parameter when starting simulations
start action payload can optionally include a
when parameter which allows the user to specify a specific start point.
when parameter holds a JSON floating point number indicating the start time in a fractional UNIX timestamp (seconds since 1.1.1970 UTC).
when parameter which lies in the past should trigger a state transition of the simulator into
state = error.
Currentlly we start the child process immediatly by spawning a new thread. A timer has to be added which schedules the execution of the process into the future.