TNL-651

does not distinguish itself from next logical line

Add new course_module field which describes what the catalog visibility should be (both, about, none)

TNL-208

 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.

STUD-1875

LMS-2737

[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]

fixing unit tests

fixing merge error

fixing xqueue submission issue with unicode url (trial 0.1)

fixing fotmats as commented upon

removing yaml file language selection

Unicode changes to support QRF

removed unnecessary pass in modulestore/init.py

fixing merge error

fixing fotmats as commented upon

removing yaml file language selection

fixing pep8 violations

- fixing pylint violations

pylint violation

fixing line spaces and formats

ignore pylint E1101

remove empty line

fixing pylint violations

 pep8 violations

bulk mail unicode/decode

fix migration error

fix pep8 just to push again

more unicode/decode
Final changes to comments and error messages.

[LMS-226]
[LMS-2013]

Replaced existing test_none_user_index_access_with_startdate_fails
test with new test now that the tested function has changed and
was causing the original test to fail.

This centralizes the logic for group membership, and means that we
don't need to make queries to find out whether the legacy groups names exist.