I think I'm completed the "Add a configuration option in the General configuration form that allows to enable/disable display of the remote user agent " step today.
Attached are screenshots of it working.
Just to make sure I didn't miss any properties file I was supposed to edit, here are the properties files I added to:
I didn't touch any of the other language property files because I don't know those languages (Pues, hablo Español tambien.)
If I missed anything just reply and I'll fix it. I'm going to start adding other User Agent images now. Cheers!