Added functionality of hiding/displaying sub-list upon click.
Added Font Awesome icons for open and closed list indicators.
Changed "information" icon (picked another Font Awesome icon).
Removed Font Awesome icons from the source tre, will download them each time.
Added plenty of comments to make code readable.

Removed unused code (`includes/`) and simplified build process.
For now, to avoid webpack overhead of 1K of code some scripts
that do not use require() have `platform = chrome` hardcoded.