LEARNER-2754

LEARNER-2977

Fixes

remove unnecessary parentheses

change css properties for mixins bi-aap in login/register page

change css properties for mixins bi-app in about course page

change css properties for mixins bi-app in the dashboard

change css properties for mixins bi-app in help template

change css properties for mixins bi-app in the home page

change css properties for mixins bi-app in jobs, press and media pages

remove the extra spaces

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.

- Doubled up :hover and :focus styling to improve a11y
- Increase contrast of certain UI elements for improved a11y
- Added some image alt text for a11y
- Changed video caption styling to blue and made them underline on hover and added a skip link before video for screenreaders.

Fixes Bugs:
- LMS-1336

LMS/Accounts: Converts many class-based Sass archetype-focused @extends to use Sass placeholder syntax

The static press page is getting edited a lot in terms of both
content and styling. I didn't want to the RSS thing until we
figured out what it's supposed to look like and need in terms of
fields. I didn't want to add a view entry, urls.py, etc. for this,
so for now it just uses an Article namedtuple inline to make
updates a little easier.

renames some scss files for better orginization, sets fixed widths on main containers to avoid akward scaling issues untill media queries can be added for more responsive scaling

cleans up home page header design, adds social sharing to header, adds tos, privacy policy, honor code, help and copyright pages, add liks to those pages in footer, finished contact page

adds pressrelease page, breaks about content into seperate pages, imporvoves some visual elements of about and jobs pages

adds banner images to and refines header on find courses pages, various visual tweeks and imporvements

refines some visual design to course objects, changes university logos on homepage, starts adding about pages and layout