core: add auto registration to qPref*

Instead of having all register calls in subsurface-helper.cpp let
qPref.cpp handle all qPref registration, since they also need to be
different

update subsurface-helper and testqml accordingly.

Signed-off-by: Jan Iversen <jani@apache.org>

core/settings/qPref.h

@@ -35,6 +35,9 @@ public:
 	static void load() { loadSync(false); }
 	static void sync() { loadSync(true); }
 
+	// Register QML
+	void registerQML();
+
 public:
 	enum cloud_status {
 		CS_UNKNOWN,
@@ -50,5 +53,4 @@ public:
 private:
 	static void loadSync(bool doSync);
 };
-
 #endif