Expand "map" type rule

The XattrMap "map" type must add automatic rules, depending on whether "key" is empty or not.

The rule ":map::prepend" must be expanded to: :prefix::prepend: :bad:all::

The rule ":map:key:prepend" must be expanded to :prefix:all:key:prepend: :bad:server::key: :bad:client:prepend:: :ok:all::

Closes #40 (closed)