Updating EX-60 logic

LMS-11235

LMS-11217

- Changes registraiton button text for professional ed courses
- Professional ed courses do not see "choose your track" page; go straight to verification flow

- Changes registraiton button text for professional ed courses
- Professional ed courses do not see "choose your track" page; go straight to verification flow

LMS-11189

 Added a new advanced setting; invitation_only

 If invitation_only display "Enrollment in this course is by invitation only"
 Otherwise, if outside of enrollment period display "Enrollment is Closed"

 This issue is logged at LMS-2670

 Also fixed in this PR is issue LMS-2717; even though the Register button was greyed out,
 clicking it sent one to the registration page.

There is an option to:
* Enable/disable accordion navigation
* Enable/disable/repoint tab navigation

This allows for full-screen XBlocks (e.g. a code IDE, or large video
player). It is also the first pass at allowing top-level XBlocks. It's
also now possible to make a chromeless XBlock, point a tab to it, and
make it point back to that tab.

Next steps down that path would be:
* Fix up how tabs are handled. The current version is a hack.
* Create appropriate XBlocks for courseware, tabbed navigation,
  etc. to reach feature parity
* Invert/rejigger the XML format.

LMS-2488

LMS-2844

Remove course_from_id
don't fetch whole course when the root will do
don't fetch even the root if the id will do
check for definition.data == null

[LMS-2757]

This commit updates lms/djangoapps/courseware.

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]

LMS-2429

LMS-2167

Changed "Status Page" -> "Page".

UX:
    support for displaying built-in tabs
    restored drag and drop on Studio Pages
    additional styling for fixed state on Studio Pages
    add a new page action added to bottom of Studio Pages

Dev
    changes for viewing tabs in studio,
    refactored the tab code,
    decoupled the code from django layer.
    is_hideable flag on tabs
    get_discussion method is needed to continue to support
external_discussion links for now since used by 6.00x course.
    override the __eq__ operator to support comparing with
dict-type tabs.

Test
    moved test code to common,
    added acceptance test for built-in pages
    added additional unit tests for tabs.
    changed test_split_modulestore test to support serializing objects
that are fields in a Course.

Env:
    updated environment configuration settings so they are
    consistent for both cms and lms.

with code to translate between addressing schemes based on app
and persistence layer addressing scheme specification.

STUD-1206

add a test case for enrollment caps

pep8 fix

Added a banner that students can use to dismiss the "you have failed reverification" message.  Also, removed unused code, wired up the sidebar for design

Also, refactored code representing ReverifyInfo