mediawiki: Enable short URLs

Currently the URLs in MediaWiki look like https://host/mediawiki/index.php/ArticleName . Instead make them look like https://host/mediawiki/ArticleName. This is done by modifying MediaWiki configuration and by updating Apache configuration appropriately.

• Update MediaWiki configuration scripts to change article path in LocalSettings.php
• Apache configuration - https://www.mediawiki.org/wiki/Manual:Short_URL/Apache
• Make sure that existing users are smoothly upgraded
• Make sure that all old URLs also work after transition