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:

- All references to the BootKAN and ks2ckan are now to the NetKAN.
- NetKAN.json no longer needed
- bin/netkan-all regenerates the entire index.
- Nicer command-line options.
- Improved `.ackrc`

Closes #151 like a boss.