UrlProvider: Introduce combine(), rootUrl(), atomFeed()

urlprovider.h

@@ -48,6 +48,12 @@ class UrlProvider
 	std::string category(std::string catname);
 
 	std::string login(std::string page);
+
+	std::string rootUrl();
+
+	std::string atomFeed(std::string filter);
+
+	std::string combine(std::initializer_list<std::string> urls);
 };
 
 #endif // LINKCREATOR_H