reformat example data files to SigMF format.

[jacobagilbert]

This adds metadata to the example recordings. I made up the RF frequencies based on reasonable values but the annotations line up nicely... though in the Mavic recording the two droneID burst frequencies are not separated by exactly 15 MHz so I am not sure precisely how the recordings were made.

https://github.com/sigmf/SigMF

[mrlnc]

Thanks! I didn't realize inspectrum actually supports this. (People reading this: you need to build the lastest version). I think we could have used SigMF as an internal format as well, looks very very good.

We need to clarify our course on PRs & contributions, so leaving the PR open for now.

[jacobagilbert]

I think SigMF would make sense as an internal format as well, and I thought about providing native support to your application but figured I'd start here. If this is accepted, and desirable, I can probably get another PR together for that - but no pressure.

[BitBangingBytes]

Applying pressure... SigMF is THE WAY! :)