NetKAN: Always use default_version_id to locate latest release.

- Includes tests.
- Closes #214.
- Thanks to @Starstrider42 for spotting this.
Merge pull request #217 from pjf/214_netkan_wrongversion

NetKAN: Always use default_version_id to locate latest release.
Added Filter and Filter Regexpes to spec and code.

They don't do anything yet.
For #129.
Added tests for filters.

As part of #129. Obviously these cause travis to fail without their corresponding code.
Add filters. Deprecate bundles and install options.

Updates the spec, the schema, and the code. Includes tests.

Closes #113 (deprecate things).
Closes #129 (add filter keywords).

This will require an update to CKAN-meta, which I've already got ready.
Fixup: Finish removing `description` field.

I only half removed it before, and caused travis to cry.
Fix numerous NetKAN JSON faults.

Our parser was apparently ignoring these, but we should be strict in our validation.
Travis validation of NetKAN files.

Also more errors discovered and corrected.
Fixed a bug where we could end up with lists of nulls.

This also means I can now install firespitter. :)