Converter for Signal Hound Recordings

[Teque5]

Originally discussed in #23, we want to implement a converter for recordings made by Signal Hound RF recorders.

• Use CLI sigmf_convert entry point and use sigmf.convert.hound.hound_to_sigmf() as entry point.
• Use sigmf.fromfile() entry point and file extension or XML parsing detection method.
• Support --archive and --ncd modes if possible
• Use example recordings in nonsigmf examples repo in test_convert_hound.py
• Add to converters.rst in Documentation

Signal hound appears to be a detached format with a pair of (.iq and .xml) so the converter will take the xyzbca.xml as the input.

[KelseyCreekSoftware]

@Teque5 - Here is the link to my preliminary SignalHound Code. It is located near the end of my project notes page.
https://github.com/KelseyCreekSoftware/KelseyCreekSoftware/blob/main/Signal-Hound-Spike-IQ-Project-Notes.md

For testing, I added a `--signalhound' arg to main:

    parser.add_argument("--signalhound", action="store_true", help="Convert a Signal Hound file pair to SigMF - provide XML file as input")

There are a number of ToDos, including determining basic information such as how to calculate the upper and lower frequency edges.

            "core:freq_lower_edge": 96000000.0,
            "core:freq_upper_edge": 104000000.0,

But at least I'm mainly using SigMFFile, for most things.

I will work on a fork, but perhaps if you create feature/signalhound I can do a PR against that branch.

[KelseyCreekSoftware]

I created a PR that may provide some possible code to draw from for this converter.
#136
Need to locate additional Spike Signal Hound files for additional testing.