Customization of CMQueryListImpl and SettingsStructToSearchQueryConverter

The Blueprint classes CMQueryListImpl and SettingsStructToSearchQueryConverter can be customized easier now by overriding protected methods, that were private before. The SettingsStructToSearchQueryConverter was enhanced by a method applyCustomFilter that can be overridden to add custom filters to the query. Additionally a custom SettingsStructToSearchQueryConverter can be provided via a new factory bean SettingsStructToSearchQueryConverterFactory .

(CMS-16276)