Add a new mode for binding widget to document properties when editing a layout.

In Studio, on the layout editor, user has three tabs on the right:

• By property
  On "By property", behavior is the same as now: user chooses schemas then properties, and drop the property on the grid.

• By widget type
  On this tab, user chooses among the list of available widget types, drops the widget on the grid and then chooses the field property in a pop up of pop up,where a tree is displayed "full screen", to choose the targeted property.

• "Advanced"
  Enable to choose template widget.