ListView bulk actions

[mmarcos]

Currently ListViews support only individual actions, available as links at the end of each row, these links are defined in the action_links property. To support bulk actions, another property bulk_action_links needs to be added. If this property is defined, then a checkbox will be displayed at the beginning of each row and if at least a row is selected then a context sensitive button/dropdown will appear on top of the listview, on the leftmost side with the available actions for the selection. This behaviour is similar to how the gmail web interface works, amongst other similar examples.