Handle ajax submit of aggregates form on select

When checking a checkbox, the form should be submitted.

Add a boolean property on select* widget types, adding a facelet handler resolving to:

f:ajax execute="@this" render="#{ajaxReRender}" listener="#{listener}"

Render ids are provided by the template rendering the layout (resolved through usual variables resolution) if possible (or use @all).

Listener will need to be hardcoded for now like Guillaume has already tested, or passed on from template displaying the layout/form to handle "default" action for more generic declaration of action to perform (inserting templating zones in all widget type handlers). Another option is to trigger the form submit in javascript and see if everything works smoothly when form is ajax-enabled.