[WIP] Bug 1036486 less2stylus

See https://bugzilla.mozilla.org/show_bug.cgi?id=1035783

[staticfiles](https://github.com/mozilla/olympia/pull/110) PR needs to be landed before.
> Being a matter of taste, we could discuss this over and over, but as the current maintainers of AMO, we made this choice, and implemented it. If you feel very strongly about that, and wish to use the syntax you prefer, please feel free to take the ticket and implement it your way, I won't fight against it ;)

While you may disagree with me, I suggest you take constructive feedback from contributors better in the future. I'm not an active contributor to AMO anymore, but I implore you to not ignore people who are trying to help. I'm thinking of future contributors and how we can reduce friction for them.