- Ensure temp files are cleaned up.
- Refactor a function with three return statements.

Fix acceptance and unit tests

LMS-1296

LMS-1296

Only do static transcript redirect for english language, and don't offer static redirect for download
Rename video test to real YouTube-ID

STUD-1558

Support incremental conversion of events from the old API to the new, in order to ensure the new system is working, enrollment events have been modified to make use of the new API.

This changes logic to allow more missed use cases of course_image to
work properly.  The cases are:

. XML courses with the course_image attribute set
. Mongo courses that are imported without a contentstore
. Mongo courses that have course_image set but don't have a content store

It also exports default images_static_course.jpg to
images/static_course.jpg to handle a use case where a course author
uploaded an image to the default location in studio without using the
studio interface for adding course images, they then export the course, and then
import it without a contentstore

BLD-662

player.getAvailableQualityLevels returns a non-empty array, it will eventually display, if HD qualities are available (highres, hd1080, hd720). [BLD-937]

LTI: Update resource_link_id to change on import to another system or context (BLD-768).