Hiding elements from inheritance

[Gulix]

Sometimes, an inherited style could need to "hide" a field / canvasField coming from the source style.

For the canvasFields, the "visible":"false" property can be used. But the field is still passed to the canvas.
For the editable fields, there is no such functionality.

Something like a "notused":"true" property could be a good idea.

[Gulix]

Documentation : http://www.gulix.fr/geckos/wiki/doku.php?id=en:template:styles#ignoring_a_parent_field