Bug 1003843 - Follow up to Bug 951676 - [Messages][Refresh] Add specific image in case of more than one recipient in the list threads. r=schung

I was thinking of something like this for things that aren't really "members" of object, but rather some non-critical-but-nice-to-have cached data... Do you think it's better to have specific property in ```ThreadListUI``` or have ```cache``` like this?