Add -moz prefixed css column styles

AN-6563 Optimized images (w/ trimage)

AN-7761 Fix broken cldr require for some languages

Commit messages for squashed debugging history:

* Update cldr libs
* Add test case for lowercasing language codes
* Rename cldr language directories to fully lowercase
* Upgrade font-awesome to 4.6.3
* Use availableLocales & silence cldr in collectstatic
* If window.language is undefined, default to "en"
* Refactor globalize to allow tests to access fixLanguageCodes
* More portable lowercasing method using tr
* Use CLDR_DATA_PATH to be more DRY
* Add mv_counter zero case message
* Change directory to cldr-data main in script
* Remove dir existence check. Doesn't work on mac
* Bring back if condition. Compare strings.
* Better solution: map lower to upper in js
* Fix the tests

Updated translations.

Add Problem Response Report Download button

AN-7640 Begin using the edX Pattern Library

replaced static with dynamically generated copyright year

* removed use of $dropdown-link-hover-bg
* update media queries to use PL variables
* update HR styles
* refactored performance chart height css
* removed unnecessary if statement in base_grouped_content.html
* updated learner analytics labelledby to be more generic

* Shorten vertical height of responsive world map
* Convert colors to pattern-library style
* Add padding to video and performance pages.
* Added padding to charts and sign in/out navbar dropdown.

* UI tweaks: performance, chart, table

* created and referencing bootstrap-components.scss

* Remove broken alert styling
* Force font-size to 100% to fix rem issue
* Use css columns for the course home page sections
* Make the world map responsive
* Fix mobile dropdown link color

* require python requirements be met before JS
* bower post-install sass compilation requires python package

AN-7774 Fix flaky a11y test

Fix waffle commands in README

Change edx-django-release-util version.

Display correct sort arrow direction on learner roster table load

Adds a "Download CSV" button to the Learner List View

Use course blocks API.

* Download CSV link shown only if waffle switch enable_learner_download is on.
* Download CSV link is styled like a button, with role=button, and href set to
  initial Download CSV link.
* Downloaded report reflects active search filters, and a configured fields
  list from settings.LEARNER_API_LIST_DOWNLOAD_FIELDS, and sets page_size from
  the total_records returned by the JSON fetch.
* Adds a learner list CSV endpoint to the learner_analytics_api, which proxies
  plain text responses from the Analytics Data API
* Reduces code duplication by refactoring BaseLearnerApiView and its subclasses
  to handle different content types

* use course blocks API for course blocks/structure
* decouple course blocks from grading policy (using original API)

A11y: Update the title element on learner page change.