This is a squash of 38 commits ending with
5b080f979d692804452400ac5bed9b17c50b001e

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.

Moved images in folders to top level where appropriate, and change references.

OPEN-297

The unused styles are referencing images that no longer exisit,
breaking collectstatic and therefore tests.

scss files that were still being partially used by the current
discussion forum.

This reverts commit 010bccc8.

Added styles to grade out the top and bottom of the sidebar border and fixed spacing with the video and the sequence nav