This reverts commit c3e1a7fa59.
Doing it this way is unnecessarily backwards-incompatible,
and there's probably a nicer way to do this.
Change-Id: Iaceeb01526004de006b4f6cb708d1e947e59090c
Used a copy of .gitignore of mediawiki/core and removed some lines,
because in this extension not all the folders which are in core.
Change-Id: I17a0a2802d1ed8b58c1096142024ec1ef12680e2