The 'theme' property

For several reasons, not least of which being the tentative nature of 
how theming will be done in future versions of XWT, I'm going to create 
a 'theme' property, handled by xwt.widget.frame (which must be preapplied).

The old:

<xwt>
     <static>
         xwt.theme( "xwt.theme", "org.xwt.theme.monopoly" );
     </static>
     <template thisbox="frame" />
</xwt>

The new:

<xwt>
     <preapply name="xwt.widget.frame" />
     <template theme="monopoly" thisbox="frame">
</xwt>

Reasons for being:
  o  More elegant
  o  Simple abstraction
  o  Solves some problems when engines/widgets are upgraded
     (no work involved for the application developer!)

Please comment / add suggestions.

- Charlie