Add attributes parameter to ShowSearchHitTitle

This would allow extensions to define custom attributes on title link,
such as put information in "title", change attributes depending on
specific search hit, etc.

Now Wikidata does the same by overriding LinkBegin, but this applies
to all links, not specifically to search result link.

Since ShowSearchHitTitle is always used with the link, I think it makes
sense to enable this specific customization.

Change-Id: I19f64e0909d92e32ddf6271f74c014e8b65d5014