Bulk captions download subs bug fix

Fixes a bug in handling bug captions where the download captions button didn't
appear on a video's view even with the option to allow caption downloads set to
true and captions properly set through the bulk captions utiltity.
The button would not appear until the studio user saved the video settings
again.

The cause of the bug was within the operation of the bulk captions
utility downloading the subtitles for a video from youtube. It correctly
downloaded and saved the subs to the database, but never set the sub field
of the video descriptor to be the id of the new subtitles saved in the
db. To fix this, a pre-existing function which handles all needed updates
is used to ensure that the sub field is properly updated along with the subs
saved in the db.
Includes management command and instructor dashboard button which gather all open assessment response data for a given course in a user friendly format and output it as a .csv

WIP finished collect_ora2_data management command, wired it to instructor dashboard UI, still needs to have logic factored out and exposed in instructor_analytics.basic

Remove extraneous print statement

Refactored sql querying logic into instructor.utils and wired the html button and management command to it there

Added comments to several methods

Added optional output_dir argument to collect_ora2_data management command and default behavior to write to stdout

Simplified code structure in management command and comments per jrbl's PR comments

Responded to jrbl's style comments, added test reference to check endpoint, and parameterized database name from django.conf.settings

Removed reference to django.conf.settings['DATABASE'] in favor of django's natural default

Removed extraneous import and whitespace per overlooked jrbl comment

Factored db connection logic into common/djangoapps/util/query.py

Whitespace changes
Merge pull request #145 from Stanford-Online/njdup/bulkcaptions_fix

Bulk captions download subs bug fix
Merge pull request #136 from Stanford-Online/dylanrhodes/ora2_instructor_button

Ora2 aggregated data download button and management command
Fix up the ora2 scores affected by the ORA2 bug: (edx/edx-ora2#628)

  For affected assessments:
    - Sets PeerWorkflowItem.scored = 0 if currently = 1
    - Recalculates the score for the submission
    - If new score > old score, update the Score.points_earned with the new score
    - Updates TrackChanges.edited_content by prepending course staff message
Merge pull request #146 from Stanford-Online/dcadams/fix_ora2_scores

Fix up the ora2 scores affected by the ORA2 (edx/edx-ora2#628) bug.
Install Image Modal XBlock from PyPi