Reset some JSF components states on ajax actions

Some JSF components keep their state between ajax actions (they are designed to behave that way).
But some ajax actions should force the reset of this state, so actions should be easily able to declare that they're resetting the state of all components in a given area.

This is useful for DAM2 where all screens are ajaxified: the faceted-search-like filter on the left needs its components state to be reset when clicking on the "clear filter" action for instance.