Test web API /stats
Test web API /stats

Added a test (test_get_stats) for the /stats web API.
This involved adding another item so that we can check both items and albums
are being counted correctly, which required a few small changes to some item
tests.

Signed-off-by: Graham R. Cobb <c27f7c700f35e8373d8cf34bd5a9d2241900fea7@cobb.uk.net>

beetbox/beets,ibmibmibm/beets,ibmibmibm/beets,ibmibmibm/beets,ibmibmibm/beets,beetbox/beets,beetbox/beets,beetbox/beets