Fixes #1650

Uses the correct exam.image relationships in Video model commit() revert() is_synched()
Changes Video edit action to properly handle exams (using exam and not exam_id in a few places)
Code that fixes #1644

All of the following changes eliminate the javascript console errors
* Re-enables the "video question" thumbnails
* Kelvinator highlighting transitions are now cued by the manifest time,
  instead of polling
* Made the cueing a separate function called in the deferred chain.
exam_feedback endpoint modeled after interactive_exercise (#1449)

Not tested yet, need to merge first.
Merge branch 'master' of github.com:Stanford-Online/class2go into sef-1449-grader

Conflicts:
	main/urls.py
#1635 in-video exams/surveys just resume video
Pass all data- elements as params for interactive exercises (#1620)
trying seeked event instead of seeking in video player
store invideo exam results back, wrong fmt (#1449)

The format of the json_data and json_score_data still aren't correct
Merge branch 'master' of github.com:Stanford-Online/class2go into sef-1449-grader
Migrations for #1513 -> make all grading fields floats
Merge pull request #1654 from Stanford-Online/jbau-jan2-fixes

Jbau jan2 fixes
Assessment student data report (#1594).

Replaces old problemset student data report with report for new exam
types.
Addendum to #1594

Tweaked the Assessment Student Data report. If the human_name for the
field is empty show the field name instead.
fixes #1598 fixes #1599 use xml to assoc video->exam
tool to merge a group of problem set reports to end up w one row per student
put the username in quotes
Merge pull request #1663 from Stanford-Online/jinpa-master-survey-merge-tool

tool to merge a group of problem set reports to end up w one row per stu...
Merge pull request #1661 from Stanford-Online/jbau-xml-video

fixes #1598 fixes #1599 use xml to assoc video->exam
Merge pull request #1660 from Stanford-Online/dca_new_working

Assessment student data report (#1594).
in video exercises: scoring feedback, hide button (#1449)