Add simple test for MRQ student_view_data 

Add docs about API methods which can be used form native apps

[OC-2874] Added choices and tips to MRQ student_view_data

They are the same as the fields found under MCQ student_view_data,
except that this is for MRQ.

Some properties which depend on user state have slipped through initial
review, so I'm removing them now.

Bumped version to 2.7.0

[MCKIN-5253] Added student_view_user_state handler

[OC-2856] Fixed deprecation warnings for the Answer and Share models

Add student_view_data to step builder

Enable mobile support

Add API for native mobile Problem Builder + MCQ view to Problem Builder

Add 'name' attribute to AnswerBlock's student_view_data.

It will be useful to be able to get the names of all answer blocks in a
course via the Course API.

Avoid count(*) query in management command.

Count(*) is very slow on large tables.

Amended headings to ensure accessibility.

* Amended templates - h2 elements to h3, h3 to h4 and associated CSS.
* Bumped version to 2.6.8

Add management command to manually migrate course_id field.

Normally the value of deprecated Answer.course_id will be copied into
the new Answer.course_key field by a migration, but if your answer table
is very large, you might want to use this management command to perform
the copying in batches instead.

Override layout of choice label in Apros theme

Do not show completion checkmark when hide_feedback is enabled