Add source properties window (very preliminary)

- Add a properties window for sources so that you can now actually edit
   the settings for sources.  Also, display the source by itself in the
   window (Note: not working on mac, and possibly not working on linux).

   When changing the settings for a source, it will call
   obs_source_update on that source when you have modified any values
   automatically.

 - Add a properties 'widget', eventually I want to turn this in to a
   regular nice properties view like you'd see in the designer, but
   right now it just uses a form layout in a QScrollArea with regular
   controls to display the properties.  It's clunky but works for the
   time being.

 - Make it so that swap chains and the main graphics subsystem will
   automatically use at least one backbuffer if none was specified

 - Fix bug where displays weren't added to the main display array

 - Make it so that you can get the properties of a source via the actual
   pointer of a source/encoder/output in addition to being able to look
   up properties via identifier.

 - When registering source types, check for required functions (wasn't
   doing it before).  getheight/getwidth should not be optional if it's
   a video source as well.

 - Add an RAII OBSObj wrapper to obs.hpp for non-reference-counted
   libobs pointers

 - Add an RAII OBSSignal wrapper to obs.hpp for libobs signals to
   automatically disconnect them on destruction

 - Move the "scale and center" calculation in window-basic-main.cpp to
   its own function and in its own source file

 - Add an 'update' callback to WASAPI audio sources

libobs/obs.hpp

@@ -63,10 +63,91 @@ public:
 };
 
 using OBSSource = OBSRef<obs_source_t, obs_source_addref, obs_source_release>;
-using OBSScene = OBSRef<obs_scene_t, obs_scene_addref, obs_scene_release>;
+using OBSScene = OBSRef<obs_scene_t,  obs_scene_addref,  obs_scene_release>;
 using OBSSceneItem = OBSRef<obs_sceneitem_t, obs_sceneitem_addref,
 						obs_sceneitem_release>;
-
 using OBSData = OBSRef<obs_data_t, obs_data_addref, obs_data_release>;
 using OBSDataArray = OBSRef<obs_data_array_t, obs_data_array_addref,
 						obs_data_array_release>;
+
+/* objects that are not meant to be instanced */
+template<typename T, void destroy(T)> class OBSObj {
+	T obj;
+
+public:
+	inline OBSObj() : obj(nullptr)    {}
+	inline OBSObj(T obj_) : obj(obj_) {}
+
+	inline ~OBSObj()                  {destroy(obj);}
+
+	inline OBSObj &operator=(T obj_)
+	{
+		if (obj_ != obj)
+			destroy(obj);
+		obj = obj_;
+		return *this;
+	}
+
+	inline operator T() const {return obj;}
+
+	inline bool operator==(T p) const {return obj == p;}
+	inline bool operator!=(T p) const {return obj != p;}
+};
+
+using OBSDisplay = OBSObj<obs_display_t, obs_display_destroy>;
+using OBSEncoder = OBSObj<obs_encoder_t, obs_encoder_destroy>;
+using OBSView    = OBSObj<obs_view_t,    obs_view_destroy>;
+using OBSOutput  = OBSObj<obs_output_t,  obs_output_destroy>;
+
+/* signal handler connection */
+class OBSSignal {
+	signal_handler_t  handler;
+	const char        *signal;
+	signal_callback_t callback;
+	void              *param;
+
+public:
+	inline OBSSignal()
+		: handler  (nullptr),
+		  signal   (nullptr),
+		  callback (nullptr),
+		  param    (nullptr)
+	{}
+
+	inline OBSSignal(signal_handler_t handler_,
+			const char *signal_,
+			signal_callback_t callback_,
+			void *param_)
+		: handler  (handler_),
+		  signal   (signal_),
+		  callback (callback_),
+		  param    (param_)
+	{
+		signal_handler_connect(handler, signal, callback, param);
+	}
+
+	inline void Disconnect()
+	{
+		signal_handler_disconnect(handler, signal, callback, param);
+		handler  = nullptr;
+		signal   = nullptr;
+		callback = nullptr;
+		param    = nullptr;
+	}
+
+	inline ~OBSSignal() {Disconnect();}
+
+	inline void Connect(signal_handler_t handler_,
+			const char *signal_,
+			signal_callback_t callback_,
+			void *param_)
+	{
+		Disconnect();
+
+		handler  = handler_;
+		signal   = signal_;
+		callback = callback_;
+		param    = param_;
+		signal_handler_connect(handler, signal, callback, param);
+	}
+};