Allow resetting some JSF components state when using ajax

There are several components showing cache issues when switching screens/pages only using ajax actions.

• a "list" widget type is caching its internal state, it is only refreshed correctly when the original data it was mapping differs, but this is not a solution for all use cases (when the initial list is empty, that does not mean that the cache can be kept, for instance)
• the nxu:valueHolder component also keeps its internal state when set
• A "shuttle" widget type using the logics made available by the SelectionActionsBean methods (to move up/down, shift from left to right, etc...) are setting the "value" attribute on selectItems components (nxu:selectItems here). This value is kept though ajax calls so are not refreshed correctly when using that kind of logics in ajaxified screens.
• maybe the chain select components --> to check

As the states need to be kept when performing ajax actions, a solution would be to define behaviours to reset the cache on some components explicitely, when performing ajax actions that changes the problematic screens.