docs: Improve man page consistency

Make Options sections refsect1 instead of refsect2, and use
uppercase for argument names. Also add a product name, and
shorten some argument names.

docs/reference/gio/gdbus-codegen.xml

@@ -1,5 +1,18 @@
 <refentry id="gdbus-codegen" lang="en">
 
+<refentryinfo>
+  <title>gdbus</title>
+  <productname>GIO</productname>
+  <authorgroup>
+    <author>
+      <contrib>Developer</contrib>
+      <firstname>David</firstname>
+      <surname>Zeuthen</surname>
+      <email>zeuthen@gmail.com</email>
+    </author>
+  </authorgroup>
+</refentryinfo>
+
 <refmeta>
   <refentrytitle>gdbus-codegen</refentrytitle>
   <manvolnum>1</manvolnum>
@@ -819,14 +832,6 @@ on_handle_hello_world (MyAppFrobber           *interface,
   </para>
 </refsect1>
 
-<refsect1>
-  <title>Author</title>
-  <para>
-    Written by David Zeuthen <email><![CDATA[zeuthen@gmail.com]]></email> with
-    a lot of help from many others.
-  </para>
-</refsect1>
-
 <refsect1>
   <title>Bugs</title>
   <para>