Add Wikidata-links to browse-helper

This pull-request adds links to the corresponding item on [WikiData](www.wikidata.org) into the browse-helper similar to the wikipedia-tags. For now it's much simpler than with the wikipedia-tags, because it only takes the plain wikidata-tag into consideration (no namespaced tags like operator:wikidata) and also restricts the values to only `/[Qq][1-9][0-9]*/`.

I'll surely add the namespaced tags mentioned on the [WikiData-proposal-page](http://wiki.openstreetmap.org/wiki/Proposed_features/Wikidata) soon, because they are quite common (Streets/buildings named after or operated by a person/organization, …).

Another thing I'd find quite interesting would be, to show the wikidata-label additionally to the link. Either next to the link and somehow visually separated to show that this label is __not__ part of the tag-value, or in the text which appears when hovering the link.
This would make it much easier for a user to "encrypt" the wikidata-values.
Would this be a good idea?
Just wanted to ask before I put work into it.