Waveform plot needs axis labels

The waveform plot added in !484 (merged) doesn't include axis labels. We should fix this.

added Good First Issue + 1 deleted label

At the same time, it would be really good to add some logger.info calls (at the very least something like "Generating waveform figure for interferometer".

The confidence levels aren't being handled properly. The default actually plots the 10% confidence interval...

mentioned in merge request !534 (merged)

added 1 deleted label

closed via merge request !534 (merged)

mentioned in commit d7b59bbd