- Have it load dates from edx-when, not just write to it. This
fixes self-paced courses where edx-when is only place dates are
kept.
- Have it read original date for a homework from edx-when when
resetting a date. This fixes the message it gives the instructor
about whether it was successfully reset.
- Have it recursively set a date, rather than assuming that dates
are only ever set on the subsection layer. This fixes setting
dates on self-paced courses (where dates are set all the way
down) and just in case somebody somewhere edits the course xml
to have a date where it's not expected.