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.

OPEN-304

* 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

* adding back in drag and drop indicators to outline DOM
* correcting visual display of drag action in outline UI
* adjusting styling of outline drag and drop indicators
* adjusting styling of drag and drop was-dropped state

styling for recursive xblock rendering structure to be used in the container page, pulling from general xblock styles in a separate file.

STUD-1186

* since Sass can now process @import rules
* to simplify the number of external calls
* maintains the http/https agnostic work
* removes unused Bree Serif font face

This reverts commit 540256b2, reversing
changes made to bd04ab5a.

Allow the fonts to be served using the same protocol as the current
page.

Also includes RequireJS changes.

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

studio - removes the .is-fleeting class/animation that is handled by backbone's min/max time for notifications

studio - reverts google web font import method back to original @font-face syntax since Sass doesn't like google's original method when processing

typography, SASS import, mixins/extends