Change linkstoimage and related messages from "link" to "use"

Change linkstoimage and related messages from "link" to "use"

These messages don't discuss links to images. For example,
[[:File:Information.svg]], which is an actual *link*, won't appear
in this list, but only [[File:Information.svg]].

As the page https://translatewiki.net/w/i.php?title=Special:Translations&message=MediaWiki%3ALinkstoimage
shows, it is already translated as "uses" to some languages.

The comparable message "globalusage-of-file" also says "use"
and not "link".

Change-Id: I659bc267240d609032a1cd2c6af479df9c09fceb