Make plots plot something initially

[kevybear]

Somebody suggested letting the plots plot something initially since having a blank canvas in a plot section could be potentially confusing. In some cases, this wouldn't work. In the compare cases feature it was built so that it would only record cases which the user selected and having it plot something when the user hasn't recorded anything could be misleading.

I think another idea would be to add text instructions to the blank canvas explaining how to use each plot. This would also be easier to implement.