Introduced top level factory class for the extension

This is an initial step in cleaning up the dependency management of this extension
- still a long way to go...

Change-Id: I2dcaada461a7d50c3713ba91a9deddce4c409650
Cleanup of the EPArticle code

* Made the EPArticle class a pure value object.
- It no longer derives from ORMRow
- All factory methods for MW objects have been deprecated

* Replaced ArticleTable with ArticleStore

* Split off code to ArticleAdder user case

* Added tests for EPArticle, ArticleStore and ArticleAdder

* Removed ArticlePager and Special:Articles

* Made code more robust and added extra checks (solves bug 46577)

Change-Id: I53a53f5b882bc8e45c16cc43b610dafe1417fea7