Unroll Article::__call

Unroll Article::__call

Add all public function from WikiPage to Article and replace the magic
__call

__call has the problem, that new functions to WikiPage will also be
available through Article.
It also makes deprecating of some functions harder. Having each function
as an own function will allow to add deprecated notice to just some and
maybe delete some functions earlier than others.

Also some static code analyzer can benefit from separately functions.

Change-Id: I779aa1c017abc9a17047fd5335f2d082148daa6f