Update object on any change in forms

[Juan Pablo Caram]

1) Check boxes and radio boxes upon change. 2) Entries upon 'enter' or action performed.

Is this critical?: Data can be lost when switching selected object.

Update on selection change? Yes.

[Juan Pablo Caram]

Updating on every change is problematic as changes originated in the code will trigger the callback as well as user changes.

For now, any code that reads the object's options should read the form (obj.read_form) first.

The options are now updated from the form every time there is a selection change (on_tree_selection_changed()). This at least ensures that no data is lost.