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/edit-xp.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'>
 	<field name="number" type='uint' top='127' left='216' width='75' height='16'/>
 	<pict type='dlog' num='2' top='8' left='8'/>
 	<text size='large' top='8' left='49' width='209' height='16'>Changing experience:</text>