Start on multiple GPUs by default (top 75 percentile by free_mem); UI selection for 'cpu' or 'auto' or a list of specific GPUs, which is now linked to the backend; Dynamically start/stop render threads for the devices, without requiring a full program restart

ui/media/js/parameters.js

@@ -73,6 +73,12 @@ var PARAMETERS = [
 		note: "warning: this will be *very* slow",
 		default: false,
 	},
+	{
+		id: "auto_pick_gpus",
+		type: ParameterType.checkbox,
+		label: "Automatically pick the GPUs",
+		default: false,
+	},
 	{
 		id: "use_gpus",
 		type: ParameterType.select_multiple,