FEAT-007: Allow work station to send "starting experiment," "experiment ongoing," "experiment stopped" signals to server

[hugomflavio]

The start signal indicates that the work station will be pinging regularly from that point on (signal could include the ping interval and how many missed pings in a row generate an alarm, or this could be fixed at the server). From that point on, the work station signals that it is still alive at regular intervals. Once the experiment is ended, the work station sends one last stop signal, terminating the process.

If the server stops receiving pings before it receives the stop signal, an alarm is issued to the app.

Experimental problems caught by this: Internet connection failure (not critical) Power outage or client malfunction (critical) Forced windows updates (critical, and stupid, but alas)

[hugomflavio]

update: Experiments need an associated ID, so the server can handle multiple experiments at the same time.

The server sends back the ID assigned to the experiment.