This also has an initial use case for Personalized Learner Schedules
to add CTAs to capa and vertical blocks to allow users to shift their
course deadlines.

- use new dates banner template on course outline page
- remove old banner from main.html
- let dates tab use new dates banner template
- remove dates banner completely from the courseware problem view
  on the web app
- use new banner on the courseware problem view on the mobile app
- update banner util to use get_course_blocks

- for self paced courses, if a sequential's due date has passed
  and it is incomplete, allow the user to reset the start_date
  for the related schedule to now, thus shifting all due dates
  for all sequentials within the course by the pre determined
  due date offset.
- add historical table to the Schedule model.

REV-980

This reverts commit 059b6197.

REV-980.
* moved get_first_purchase_offer_banner_fragment to Discounts utils.py
* added banner wrapper method
* updated banner with time limit 

Moves banner into the content instead of at the top. Adds a course
expiration fragment to the course home page, the content, the progress
page, and the discussion page.

update css

updated css

make modal experimental

add waffle flag

LEARNER-2977

Fixes

LEARNER-142

to the Micromasters page

LEARNER-1705

LEARNER-1694

Fix a11y failure

Fix header styling

Fix layout issues

Further layout fixes

FEDX-375

LEARNER-1890

LEARNER-1785

This story was to update the existing custom themes to work with the flexible bootstrap design. It also updates the red theme to more closely resemble the real implementation on openedx.

LEARNER-1174