allow testing multi_client on remote db. must authenticate and have permissions to create/drop db
honor MONGOOSE_SKIP_DROP on all db drops, allows testing on existing
test db with user credentials (caveats: leaves a mess, and multi_client
test probably won't work because requires permission to create db)
add -Ilib to tests via prove
add optional auth_db_name param for auth against db other than one with
collections
update POD
another POD tweak