New JSON-source build tool

This is a huge update. I've created a new JSON schema (see [here](https://github.com/browscap/browscap/wiki/Proposal:-JSON-Source-File-Schema)), which this new tool uses. The proposal I've created attempts to simplify contributions via GitHub - people can fork the repo, edit the JSON, build their own INI files to test, create a Pull Request back to us. The aim of this is to give anyone the ability to help update the INI files, although having the actual files generated by the few project owners.