(SOL-531)(SOL-532)Course Cards update; A link to course discovery page has been added to the OpenEdX homepage

[LMS-11372]
[LMS-11370]

This commit updates lms/templates.

These keys are now objects with a limited interface, and the particular
internal representation is managed by the data storage layer (the
modulestore).

For the LMS, there should be no outward-facing changes to the system.
The keys are, for now, a change to internal representation only. For
Studio, the new serialized form of the keys is used in urls, to allow
for further migration in the future.

Co-Author: Andy Armstrong <andya@edx.org>
Co-Author: Christina Roberts <christina@edx.org>
Co-Author: David Baumgold <db@edx.org>
Co-Author: Diana Huang <dkh@edx.org>
Co-Author: Don Mitchell <dmitchell@edx.org>
Co-Author: Julia Hansbrough <julia@edx.org>
Co-Author: Nimisha Asthagiri <nasthagiri@edx.org>
Co-Author: Sarina Canelake <sarina@edx.org>

[LMS-2370]

If neither start nor advertised_start has been changed from default
don't show the course start date.

This allows us to accept course registrations for courses whose start
date is yet TBD.

The course’s university was displayed using a <a> tag that points to
nothing ('#'). There was some stanford specific behavior to replace that
<a> tag with a <span>. This commit removes that.

Remove unused course_filter page

removes university_profile urls and templates

removes all university_profile views

remove news from templates/index

Adjust the now-defunct landing page so that it doesn't render much
of the edX-specific marketing info (social links, press releases,
university partners, etc.) if a theme is enabled.

Additionally, if the Stanford theme is enabled, add in some school-
specific language and adjust the video modal to play a Stanford one.

The property can be set in the policy metadata. If it is not specified
then it is set to true if the course has not started yet.

Also adds a property to check how many days are left until the course starts.

Added {COURSE_STATIC_URL} format key for about section html. Changed get_about_section to be get_course_about_section in courseware.courses.

The about image is now pulled from the course data directory and shown on the homepage, about course, and dashboard. Working on a way to show other, arbitrary course images.

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

This reverts commit 05e1bcf4.

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