Be able to display JIRA charts inside XWiki

See https://forum.xwiki.org/t/brainstorming-xwiki-10-x-cycle-roadmap/2274/9?u=vmassol

See also this old GSOC project that tried to make XWiki an opensocial container: http://markmail.org/message/bxxrwdkilqf6lrwe

See also https://confluence.atlassian.com/doc/registering-external-gadgets-204050482.html and https://confluence.atlassian.com/display/GADGETS/Introduction+to+Atlassian+Gadgets+and+Dashboards

So the issue for XWiki as I see it is to implement opensocial which is deprecated...