Various tweaks and modernization

* Swapped addModules() to addModuleStyles() since the only RL module contains nothing but a CSS file
* Converted from PHP i18n to JSON
* Got rid of $dir / dirname( __FILE__ )
* Updated hooks and their signatures, namely swapped ArticleSaveComplete to PageContentSaveComplete
* wfMsg -> wfMessage
* Bumped version number to 1.23, just because

Change-Id: Ia4e6be60db0353eb5af8b1a9f61922c75eee2b26