Metrics download (task: CE-505)

Ability to download metrics reports in png and csv format.
All methods, which related to getting of url from object ``` F::app()->wg->title ``` - returns urls, which contains additional params as a part of url path (e.g. ``` /wiki/Special:NewWikisGraph/pl ```)

And in case of creation of instance of Title object in the following way ``` SpecialPageFactory::getPage( self::NEW_WIKIS_GRAPH )->getTitle() ``` - there is an ability to get url, without params (e.g. ``` /wiki/Special:NewWikisGraph ```)

So, this fix helps to solve issue with uncorrectly generated urls. 

(This code appeared here, by the reason of branching from the: https://github.com/Wikia/app/pull/4082)