Verify submission_uuid when creating assessments

This corrects an issue where assessments were sometimes incorrectly
associated with the wrong response.

The behavior was caused because the POST request to the `peer_assess`
handler only contained the feedback text/options and did _not_ include
mention of which original response was being assessed. If the current
workflow item is updated on the server _after_ the page first loads but
_before_ the page is submitted, this submission will be incorrectly
associated with the following response.

Steps to reproduce:
- Submit a response (User A).
- Wait for peers to submit responses (User B and User C).
- Load page with first peer response to be assessed (not not submit).
- Open the same page again in a new tab.
- In 1st tab, assess and submit assessment for User B.
- In 2nd tab, assess and submit assessment for User B.
- Notice that your assessment for User B's response is also applied to
  User C's response.

This changeset does _not_ restore data retroactively.

Fix TNL-680

Update lxml and scipy

Don't pin the version too strictly.

Update Transifex translations

Don't use published_date to figure out if xblock is published

ask the modulestore if it's published
LMS-11184

Fix typo

Add updates about image responses, including screen shots

MathJax Integration

Currently, Latex rendering is only supported for question prompts in ORA2. This
commit introduces Latex rendering in ORA2 student response, peer assessment
view, self assessment view, grade view, and staff-info view. The reason that
this Latex rendering code is inserted directly into ORA2 is that edx-platform,
does not know when to start Latex rendering for ORA2 views that come in via
AJAX.

This commit introduces "Preview in Latex" feature which allows students to see
their response rendered in MathJax before submission.

Conflicts:
	openassessment/xblock/static/js/openassessment-lms.min.js
	openassessment/xblock/static/js/openassessment-studio.min.js

Instructors can edit default response feedback text

Previously, instructors were unable to edit the feedback prompt text ("I noticed that
this response...") displayed in the response box asking a student to provide feedback
on the peer responses they received.

To allow instructors to edit this, I've added an editable xml element (feedback_default_text).
The text within the element defaults to "I noticed that this response...," but an instructor
can change this text to whatever he or she wants by editing the text within the xml element.

Editing of this new element has also been added to the authoring gui.

Added image display in leaderboard

Will/top scores fixups

Fix loading step CSS location

Sylvia/docs/ora 65

Note for DNS friendly buckets

Inline badges

Update readme to include dev docs link and remove DEBUG_JS reference