Enable freeform answer submit when feedback is hidden

When problem builder is configured to hide feedback upon revisiting a question
(pb_hide_feedback_if_attempts_remain option is enabled), when the user returns
to a problem builder block which contains only a freeform question,
the user is not able to click "Submit" without changing the answer text first.

This patch fixes that by keeping submit button enabled if
pb_hide_feedback_if_attempts_remain is turned on.

MCKIN-3890

StepBuilder: Fix inconsistent feedback for MCQs

When the pb_mcq_hide_previous_answer is set to True, MRQs should behave
the same way as MCQs behave - previous choices should not be displayed
and the checkmarks should be hidden.

Add instructions for enabling dashboard in studio

Use dashboard image from master branch in tests

So that the omar/report-download branch can be deleted

Fix dashboard report image download

Restore functionality for showing choice tips on click

Problem Builder: Add instance-wide option to hide global feedback and results for Long Answer blocks

- More neutral default for "get_option"
- Separate integration tests for checking persistence behavior

feedback should be shown when student returns to block.

The new setting is called "pb_hide_feedback_if_attempts_remain".

When set to True, Problem Builder blocks will not show global feedback
messages (as long as one or more attempts remain), and will hide
results (correct/incorrect icons) for Long Answer blocks.

OC-1387 Always show tooltips feedback if tips are present.

Ensure default theme is used if theme has not been customized

Problem Builder: Add instance-wide option to hide previous answers for MCQs

- Refactor: Take advantage of mixins from xblock-utils accessing xblock settings.

- Fix existing tests.
- Add unit tests for code that deals with instance-wide options.
- Add integration test for scenario where previous answers for MCQs are configured to be hidden.

MCQs are shown when users revisit them.

blocks works in both Apros and the LMS.

Fix exponential rerendering after hitting next button too many times.

Bump version.

Implement Django Migrations

Create Django migrations, deprecate South.