Focusable label element widgets

<element id="directory-name">
  <focusable_label type='theme_text'>Top Level Directory</focusable_label>

  <options>
     <widthmm>40</widthmm>
     <focus_border>custom</focus_border>
  </otions>
</element>

Specifying an element with a focusable_label creates a new theme widget which is an x::w::focusable_label widget. This is equivalent to invoking the factory's create_focusable_label() method.

The focusable_label element has the same contents as a label element, with an additional options setting. options initializes the x::w::focusable_label_config parameter for create_focusable_label, which has the same members as label's x::w::label_config, with an additional focus_border that sets the focusable label's appearance object.