Support single and double quotes in xblock string field editor

Addresses STUD-1984. @cahrens @andy-armstrong please review.
I wouldn't remove all of these tests. We want to verify that the display name is inline editable for the container page. The fact that the inline editing view works as a unit doesn't mean that it is correctly configured inside the container page. It may be that you can inline edit but the value doesn't get saved. In fact, there's nothing stopping someone from removing the inline editor entirely in the future and we wouldn't know.

There is a fine line here with having too many duplicate tests but I think removing them all is going too far. I would entertain the idea that some of these are now unnecessary although looking at them I'm not sure which subset I'd remove.