assign escbtn and defbtn appropriately

Behaviorally: This change makes it so that Enter will never cancel
a dialog, unless that dialog only contains info to be read. Escape
will never unpredictably be treated as Enter. And some dialogs without
Escape to cancel, now can be canceled with Escape.

A lot of this just refactors dialogs to define the cancel button
at the top, not as a hotkey on a cancel button deep in the XML.
I think this makes enter/escape behavior in dialogxml files more
legible at a glance.

rsrc/dialogs/edit-vehicle.xml

@@ -1,6 +1,6 @@
 <?xml version='1.0' encoding='UTF-8' standalone='no'?>
 <?xml-stylesheet href="dialog.xsl" type="text/xsl"?>
-<dialog defbtn='okay'>
+<dialog defbtn='okay' escbtn='cancel'>
 	<pict type='dlog' num='16' top='8' left='8'/>
 	<text name='title' size='large' rel-anchor='prev' relative='pos pos-in' top='-2' left='6' width='256' height='17'>Edit Vehicle</text>
 	
@@ -18,7 +18,7 @@
 
 	<led name='owned' anchor='name-lbl' relative='pos-in pos' top='11' left='10'>Not Party Property</led>
 	
-	<button name='cancel' rel-anchor='prev' relative='neg pos' type='regular' def-key='esc' top='15' left='10'>Cancel</button>
+	<button name='cancel' rel-anchor='prev' relative='neg pos' type='regular' top='15' left='10'>Cancel</button>
 	<button name='del' rel-anchor='prev' relative='pos pos-in' type='regular' top='0' left='0'>Delete</button>
 	<button name='okay' rel-anchor='prev' relative='pos pos-in' type='regular' top='0' left='100'>OK</button>
 </dialog>