Add Cabrillo output

[nmote]

This will require:

• Support for more log entry fields
• A mechanism by which to limit the fields that are included in the output (for the sake of not bloating the POTA output)
• A CLI interface to choose the output kind
• Some mechanism by which to handle the header data needed in Cabrillo logs

[nmote]

Most of this is pretty straightforward, the challenging part is figuring out how to create a reasonable interface to provide the header data. It's too much data to be suitable for command line arguments, and it doesn't fit neatly into a CSV where you expect every row to have the same basic format. A couple options are:

• Allow users to provide an incomplete Cabrillo file containing only the header data as a separate input
  • The caveat is that this isn't very user-friendly, and they may make mistakes. So, we'd have to read and validate the given Cabrillo file to catch typos or missing required header fields.
• Create some sort of way to represent the header items as rows in the CSV
  • The upside here is that there would still be only one main input, and people wouldn't have to learn any details about the Cabrillo format.
  • The caveat here is that this sort of thing doesn't lend itself neatly to CSV, so there would have to be some sort of contrived format to allow for the header fields, which might be hard for people to understand. It probably wouldn't be any worse than making them provide a separate partial Cabrillo file, though.