(mu-bbdb-get-attr): Renamed.

(mu-bbdb-get-attr): Renamed.
(mu-bbdb-set-attr): Renamed.
(mu-bbdb-get-prefix-method): Renamed from
`mu-cite/get-bbdb-prefix-method'; add DOC-string.
(mu-bbdb-get-prefix-register-method): Likewise.
(mu-bbdb-get-prefix-register-verbose-method): Likewise.
Delete setting for `mu-cite/default-methods-alist'.