Allow users to see course materials by section from dropdown #858

Extends get_course_materials function to return materials for single
section. Meant for viewing live sections, thus why there is no dropdown
for instructor's edit view.
interactive autograder: log on call, more exceptions (#1729)

Also fixed an unqualified exception.
gather associated text: trim whitepace and odd chars (#1729)
#1530 - move scoring to the correct tables.

Removes appropriate:
ExamRecordScore
ExamRecordScoreField
ExamRecordScoreFieldChoice

Creates new:
ExamRecordScore
ExamRecordScoreField

Updates score in:
ExamRecord
ExamScore

Also, I replaced the colons in the export file names with dashes as
colons are not good in Windows file names.
Merge branch 'master' of http://github.com/Stanford-Online/class2go into
dca_new_working2

Conflicts:
	main/courses/exams/views.py
Grade export files contained a blank line at the end that was causing an
warning on import. Removed the blank line if file was going to be larger
than zero size. The blank line is still needed for otherwise zero length
files as S3 throws an error.
fixes #1728 adds ordinal numbering
Fix for #1713

Hide explanations when transitioning to new questions, redisplay when
Check Answer clicked

	modified:   templates/exams/videotest.js
	modified:   templates/exams/view_exam.html
Merge pull request #1735 from Stanford-Online/wescott-master-1713-fix

Fix for #1713
Merge pull request #1734 from Stanford-Online/jbau-ordinal-numbering

fixes #1728 adds ordinal numbering
Refactor left_nav.html for improved readability

* Partial rewrite of get_full_contentsection_list for improved
  concision, readability, and to change the shape of full_index_list:
 * Instead of a sorted list of lists of tuples, it is a dictionary of
   sorted lists of dictionaries. This allows for nicer lookups in
   left_nav.html with less iteration overall.
* Update to left_nav.html to take advantage of this change. Also
  introductes local variable value caching using {% with %}
* Introduction of byKey template filter, which allows lookup into a
  dictionary by tha value of a template variable, rather than by its
  name: i.e., 'somedictionary|byKey:variable' will return
  somedictionary[variable] rather than somedictionary['variable']
* Correction of {% url %} reverse for exams in left_nav.html
  (fixes #1630)
File format change from DOS to Unix
Merge branch 'master' of http://github.com/Stanford-Online/class2go into dca_new_working2
Merge pull request #1733 from Stanford-Online/dca_new_working2

Move CSV scoring to the correct tables #1530
Connection in own function; granular exceptions handling (#1729)
Chris exercise conversion script (#1729)

Squirreling away here for good measure.
Merge branch 'master' of github.com:Stanford-Online/class2go into sef-1729-interactive-exercises
#1740 - Mark db records as "csv imported"

ExamRecordScore
ExamScore

This causes a migration.
Merge branch 'master' of http://github.com/Stanford-Online/class2go into dca_new_working2
Merge pull request #1742 from Stanford-Online/dca_new_working2

#1740 Mark db records as "csv imported"