CSV Reporting of Shopping Cart Purchases, with tests

squashing to one commit to make cherry-picking by feature possible
Events for entering verified flow & buying
Update course_navigation.html

The tab names are not being translated
fixed the path to the header example image in the Studio html editor help sidebar
STUD-981
Make remaining dialogs in wiki accessible.

All the dialogs in the wiki are now accessible to screen readers.

Also, the "Switch to selected version" button did the odd thing of
reloading the page with the new version selected, but inside a dialog.
That is now fixed.

The merge dialog has a warning that looks kind of funky still, but you
can read it, unlike the previous code.

LMS-1337
Update mode appropriately when user enrolls

The "mode" was remaining unchanged when a student unenrolled & re-enrolled in a course--i.e., someone who was verified when first registering would still be verified when unenrolling and re-registering in audit mode.  This commit fixes this problem.

LMS-1526
Upgrade coverage to 3.7
LMS: adds in collapse/expand UI for dashboard view upsell
Changed unit identifier to be readonly, not disabled

STUD-863
Added refund datetime info to Orders, OrderItems

Finance would like to have info about the date any given refund is requested.

This commit adds a refund_requested_time field to OrderItem and a refund_time to Order.

When a user *requests* a refund, the refund_requested_time field on OrderItem is updated; when a user actually *receives* their refund, the refund_time on Order is updated.

Note that only the refund_requested_teim field is actually used right now; later on, when we're able to actually automate the process of actually giving users refunds, we will start usings Order's refund_time field.
Studio: correcting hiding state of notification UI for < IE9
STUD-815
Fix unique vertical url + add test
STUD-979
Restful api for course advanced settings
STUD-948
Disabled video caption tests that failed in master
Studio: adding basic italicize text styling into xmodule/block preview UI
STUD-963
Disabled another video test that failed in master
Response to CR
Quick fix
Remove code related to Pearson Testing Centers
Rebase to re-prepare PR