Qtfred ship texture replace refactor

qtfred/help-src/doc/dialogs/ShipTextureReplacementDialog.html

@@ -24,11 +24,13 @@ <h2>Other Maps</h2>
 <ul>
     <li><strong>Replace</strong> - check to enable a replacement for this map
         type.</li>
-    <li><strong>Inherit</strong> - automatically derives the replacement name by
-        appending the map type suffix to the main texture replacement name (e.g.
-        replacing <code>fighter01</code> with <code>myfighter</code> and inheriting
-        the normal map produces <code>myfighter-normal</code>). Uncheck to enter the
-        name manually.</li>
+    <li><strong>Inherit</strong> - when checked (the default), automatically derives
+        the replacement name by appending the map type suffix to the main texture
+        replacement name (e.g. replacing <code>fighter01</code> with
+        <code>myfighter</code> and inheriting the normal map produces
+        <code>myfighter-normal</code>). Uncheck to enter a custom replacement name
+        for just this map type; the name field becomes active when Inherit is
+        unchecked.</li>
 </ul>
 <p>Models that only define a base diffuse texture will show no controls in this
 section.</p>