FIX for nested widgets with data-parts

invoking a widget with data-part overrides within a data-part does not work.

example:
&lt;div data-bind="widget: outer">
&nbsp;&lt;div data-part="outer-widget-part">
&nbsp;&nbsp;&lt;div data-bind="widget: inner">
&nbsp;&nbsp;&nbsp;&lt;div data-part="inner-widget-part">
&nbsp;&nbsp;&nbsp;&nbsp;this will not take effect
&nbsp;&nbsp;&nbsp;&lt;/div>
&nbsp;&nbsp;&lt;/div>
&nbsp;&lt;/div>
&lt;/div>

reason: the outer widget consumes the data-part of the inner widget.

solution: ignore data-parts within widget bindings