[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.
who finds that more comfortable? this format is completely unreadable to me, and I write a lot of CSS. if you want to reduce friction for contributors, consider using a syntax that is more similar to the syntax that people are already familiar with.