String changes in yelp

[Shaun McCance <shaunm gnome org>]

I've just committed two string changes to yelp.  The first is the string
"Unknown Section".  This is used effectively the same way as the string
"Unknown", which should no longer show up.

The second is the string "Multimedia".  This replaces the string "Sound
& Video".  This is the name of the category of documents, which should
correspond to the submenu under the gnome applications menu.  I had put
"Sound & Video" because that's what my machine says.  But it turns out
that's a Fedora change, and the upstream word is "Multimedia", so I've
change it to be the same as the upstream menu.

--
Shaun