dvcc: add setting for control of all multis

Originally DVCC parameters were used only to control one
Multi or Quattro. A new feature in systemcalc makes it
possible to control all of them, in systems where there
may be more than one. To avoid sudden changes in existing
systems, it is an option that defaults to off.

victronenergy/venus-private#479

pages/settings/PageSettingsDvcc.qml

@@ -211,6 +211,31 @@ Page {
 					uid: bmsName.serviceUid ? "%1/CustomName".arg(bmsName.serviceUid) : ""
 				}
 			}
+
+			ListSwitch {
+				//% "Managed battery controls all Multis and Quattros"
+				text: qsTrId("settings_dvcc_control_all_vebus_devices")
+				dataItem.uid: Global.systemSettings.serviceUid + "/Settings/SystemSetup/DvccControlAllMultis"
+				allowed: defaultAllowed && commonSettings.dvccActive &&
+						 nrVebusDevices.isValid && nrVebusDevices.value > 1
+
+				bottomContentChildren: [
+					PrimaryListLabel {
+						topPadding: 0
+						bottomPadding: 0
+						color: Theme.color_font_secondary
+						//% "When enabled, the managed battery controls all Multis and Quattros. "
+						//% "When disabled, only the device on the built-in port is controlled. "
+						//% "See documentation for further information."
+						text: qsTrId("settings_dvcc_control_all_vebus_devices_label")
+					}
+				]
+
+				VeQuickItem {
+					id: nrVebusDevices
+					uid: Global.system.serviceUid + "/Devices/NumberOfVebusDevices"
+				}
+			}
 		}
 	}
 }