edx-dl: Don't use small options for infrequent functions.

We don't want to pollute the potential uses of `-d` being used for a better
purpose in the future, even if that use is to restore back our the debugging
semantics.
edx-dl: Try many styles for extracting video IDs.

We can possibly expect to add some newer strategies/formats for the future,
as the dust settles with edX choosing a stable method, but we will probably
have to keep all of them in the case of trying to support sites that employ
edX's platform, but that don't upgrade as often as edX does.