HG-117: Added rtl support

Foundation docs state that adding the proper language and direction in the header is enough for `rtl` support
http://foundation.zurb.com/docs/components/rtl.html
Partially. `languageDirection` depends on the user's language or the wiki language if the first one is not set, so this takes care of the whole interface. On the article level we have to explicitly set the direction of the content.