Allow selection of different stream variants in the player (#815)

* WIP video quality selector

* The quality selector works even though it is not pretty

* Support getting and setting variant name. Closes #743

* Sort video qualities

* Fix odd looking selected states of menubutton items

* Fix comment

router/router.go

@@ -58,6 +58,9 @@ func Start() error {
 	// return the logo
 	http.HandleFunc("/logo", controllers.GetLogo)
 
+	// return the list of video variants available
+	http.HandleFunc("/api/video/variants", controllers.GetVideoStreamOutputVariants)
+
 	// Authenticated admin requests
 
 	// Current inbound broadcaster