SemanticMediaWiki.hooks clean-up

Added:
- SMW\MediaWiki\Hooks\ResourceLoaderGetConfigVars;
- SMW\MediaWiki\Hooks\GetPreferences;
- SMW\MediaWiki\Hooks\SkinTemplateNavigation;

Removed:
- `onParserTestTables` which was never used
Merge pull request #422 from SemanticMediaWiki/hooks-tidy

SemanticMediaWiki.hooks clean-up