Provide an API to retrieve the highest embassy level (possibly not counting
a given body_id) so that we can determine if an alliance leader could possibly
downgrade or demolish a given embassy.
Create a couple of short-cut methods to make testing via one-liners easier:
Lacuna->db->empire(name_or_id) and Lacuna->db->building(id).  This may
also be useful for new scripts, whether AI or otherwise.
Return the building ID for the empire's favourite embassy (if any) as part
of the empire's status.
Remaining downgrade/demolish leader's embassy code.
Stylistic changes
Fixed bug with DEPRECATED 'single' method