Infobox description editing

To test:
* Make sure you are using an account you created after setting up Wikidata instance
* Create item on http://wikidata.wiki.local.wmftest.net:8080/
* In LocalSettings.php
** Set $wgMFWikiDataEndpoint = 'http://wikidata.wiki.local.wmftest.net:8080/w/api.php';
** Set $wgCrossSiteAJAXdomains = array( '*' );
* Navigate to page http://localhost:8080/wiki/Albert_Einstein?wikidataid=<item number>

Change-Id: I87c9deec5dd3efafd98ff43298a7cfaf4e1dcbb4
Merge "Infobox description editing"