SASS compilation variable conventions update, focusing on basic colors, baseline variable usage for padding and margins, ui-depth extends, along with other small fixes. The intent with this is to not have any user-facing impact, and instead move us closer toward having files that use our newer sass conventions.

* removing unused font-family-centric Sass variables
* removing unused graphic images and Sass references
* clean up of style removal fallout

* moving font-size to use @include font-size() mixin
* re-organizing vendor reset styling into _vendor.scss override rather than _reset.scss
* initial rule re-organization and minor line-height tweaks

Also includes RequireJS changes.

Fixes bugs:
STUD-755, STUD-152, STUD-700, STUD-699

Bourbon's box-shadow mixin has been deprecated, and they recommend to use the
official spec.

The official border-radius mixins were deprecated and removed in Bourbon 3.0.
https://github.com/thoughtbot/bourbon/pull/95

studio - adds back in older lh() Sass function/mixin and moves it to the inheritied/to-be-sunsetted mixins sheet

typography, SASS, imports

typography, SASS import, mixins/extends