All dialogs now use default skin and foreground colour

(The attributes are still available in the schema though, and will not be removed.)

rsrc/dialogs/need-party.xml

@@ -1,6 +1,6 @@
 <?xml version='1.0' encoding='UTF-8' standalone='no'?>
 <?xml-stylesheet href="dialog.xsl" type="text/xsl"?>
-<dialog skin='dark' defbtn='okay'>
+<dialog defbtn='okay'>
 	<button name='okay' type='regular' top='52' left='256'>OK</button>
 	<pict type='dlog' num='16' top='6' left='6'/>
 	<text top='6' left='49' width='273' height='43'>