bug 2503: tests for C4::Circulation

bug 2503: tests for C4::Circulation

I'm adding some tests for C4::Circulation methods that I'm altering
to allow the offline circulation tool to use C4::Circulation to upload
its data. These test a bit of the old functionality and try to show
that the new functionality does what I think it does.

C4::Circ::Addissue to tests issuedate
 these also test AddRenewal.
tests for C4::Circ::MarkIssueReturned

Signed-off-by: Galen Charlton <galen.charlton@liblime.com>