waveform branch: imagine header issue

[Cody-G]

According to our usual .imagine file standard, piezo start and stop position should be specified with length units like this: piezo=start position: 0 um;stop position: 200 um

Here's a full example file: https://github.com/timholy/ImagineFormat.jl/blob/master/test/test.imagine

@kdw503 It seems that recent changes to the waveform branch may have dropped units from this line in the header.

[Cody-G]

This seems fixed so I will close, thanks @kdw503