Update for AMO prerequites

AMO requires maxVersion not to be * (
https://addons.mozilla.org/en-US/firefox/pages/appversions/ )

Also added em:type to get rid of an AMO warning

install.rdf

@@ -16,7 +16,8 @@
       <Description>
         <em:id>{ec8030f7-c20a-464f-9b0e-13a3a9e97384}</em:id>
         <em:minVersion>3.0</em:minVersion>
-        <em:maxVersion>*</em:maxVersion>
+        <em:maxVersion>41.0</em:maxVersion>
+        <em:type>2</em:type>
       </Description>
     </em:targetApplication>
   </Description>