Work in progress.

- Generate license definition file as data/licenses.json, for each license:
  1. Store the licensedb identifiers.
  2. Store whether the license is free/libre or not.
  3. Parse license text fragments from li:notice/li:text fields.
Preliminary support for @licstart / @licend license block.
Grab librejs magnet urls from licensedb.
README fixes and include test files.