With this commit, the prefixed wikidata-tags get linked to the
corresponding wikidata.org-page in the current interface-language.
Multiple semicolon-separated wikidata-IDs are shown as multiple
semicolon-separated links to wikidata.
This commit contains also some tests for those links.
It turns out that the PHP urlencode encodes more characters than
the ruby URI.encode does by default, so specify our own characters
to encode based on http://php.net/manual/en/function.urlencode.php
with the extra exclusion of colon, which the mediawiki code reverses
after the encoding is done.
Fixes#967
International phone numbers become links using the official URI scheme
as per http://tools.ietf.org/html/rfc3966.
It is not limited to key=phone, so it can be used in other keys as well.
