(TopLevel): Use `mu-cite-default-methods-alist' instead of

(TopLevel): Use `mu-cite-default-methods-alist' instead of
`mu-cite/default-methods-alist'.
(mu-cite/get-bbdb-prefix-register-method): Use `mu-cite-minibuffer-history'
instead of `mu-cite/minibuffer-history'.
(mu-bbdb-get-prefix-register-verbose-method): Use `mu-cite-get-value' instead
of `mu-cite/get-value'.
(mu-bbdb-get-prefix-register-method): Likewise.
(mu-bbdb-get-prefix-method): Likewise.
(mu-bbdb-load-hook): Use `defcustom' instead of `defvar'.
(mu-bbdb): New customization group.
(TopLevel): Define old functions as obsolete aliases.
(mu-bbdb-set-attr): Renamed from `mu-cite/set-bbdb-attr'.
(mu-bbdb-get-prefix-register-verbose-method): Renamed from
`mu-cite/get-bbdb-prefix-register-verbose-method'.
(mu-bbdb-get-prefix-register-method): Renamed from
`mu-cite/get-bbdb-prefix-register-method'.
(mu-bbdb-get-prefix-method): Renamed from
`mu-cite/get-bbdb-prefix-method'.
(mu-bbdb-get-attr): Renamed from `mu-cite/get-bbdb-attr'.
(TopLevel): Require `path-util' for picking up `module-installed-p'.
(TopLevel): Require `cl' at the compile time.
(Keywords, Maintainer): Add comments.
(Author): Change mail address.
(Copyright): Belong FSF.