Edits tested using clean FW v2.60~39 install

1	used relaystate.py from FW 2.33
2	edit /etc/venus/gpio_list
	- added relay_2 -> OK
3	reboot -> relay_2 appeared in the GUI and works
4	edit /etc/venus/gpio_list
	- added relay_3 -> OK
5	reboot -> relay_3 NOT appearing in the GUI
6	edit /opt/victronenergy/gui/qml/PageSettingsRelay.qml
	- added to MbPage section:
		property VBusItem relay2Item: VBusItem { bind: "com.victronenergy.system/Relay/2/State" }
		property bool hasRelay2: relay1Item.valid
	- added to MbSwitch section:
		MbSwitch {
		id: manualSwitch2
		name: qsTr("Relay 3 On")
		bind: "com.victronenergy.system/Relay/2/State"
		show: hasRelay2
		}
7	reboot -> relay_3 appeared in GUI and works correctly
8	edit /etc/venus/gpio_list
	- added relay_4 -> OK
9	edit /opt/victronenergy/gui/qml/PageSettingsRelay.qml
	- added to MbPage section:
		property VBusItem relay3Item: VBusItem { bind: "com.victronenergy.system/Relay/3/State" }
		property bool hasRelay3: relay1Item.valid
	- added to MbSwitch section:
		MbSwitch {
		id: manualSwitch3
		name: qsTr("Relay 4 On")
		bind: "com.victronenergy.system/Relay/3/State"
		show: hasRelay3
		}
10	reboot -> All four relays available in GUI and operational.