[UI] Plot the data from one measurement

[romain-jacob]

In practice, it would be useful to have a quick way to see the datapoints in a measurement. Especially for clean-up of automatically created measurements while setting up. A plot would quickly give that.

Another (more lightweight approach) would be to query the first and last few datapoints of a measurement without having to download the entire thing. That would do the trick just fine, actually. The main info one needs to know if a measurement must be kept are the timestamps, no need a full plot for that.