The all new and amazing NetKAN!

We can now inflate files with `netkan SomeMod.ckan`. Provided it
contains a `$kref` path we recognise, we'll fill in the metadata,
validate it, and write it out (`SomeMod-1.23.ckan`).

We support both KerbalStuff IDs, and Github repos:

- `"$kref" : "#/ckan/kerbalstuff/269"`
- `"$kref" : "#/ckan/github/pjf/DogeCoinFlag"`

Other changes include:

- BootKAN -> NetKAN (directory rename)
- NetKAN.json no longer needed
- bin/netkan-all regenerates the entire index.
- Nicer command-line options.