[miele] Fix stateless stop channel and synchronize switch channel from state

[jlaur]

Channel stop should be changed to auto-update policy veto since it's a stateless channel with the purpose of triggering a stop action (for oven and hood). This will eliminate the need for configuring autoupdate="false" on the item.

Channel switch is used either for triggering start/stop actions or actually switching appliance on or off. Since it has this duality, it's by definition not stateless. However, the state is not initialized, so when an appliance is actually turned on, the channel might be set to false, depending on last manual value change. This should be fixed so that current state is used to set state correctly.

Additional notes:

• For my oven, H5581BP, the switchOn/switchOff methods doesn't actually work. Probably switchOn will not work for any oven due to Miele security policy, but switchOff could potentially work on other models. If not, there is no reason for having the channel at all. The stop method turns my oven off (as opposed to just stopping running program). This method as exposed separately in channel stop.
• The switchOn/switchOff methods are also supported by coffee machines, but I don't know if they actually work. @PaulchenP, perhaps you can verify if you can turn your coffee machine on and/or off using the switch channel?
• Dishwasher/washing machine/tumble dryer implements the switch channel as start/stop methods (as opposed to switchOn/switchOff).
• For tumble dryer I have verified that start/stop works (exposed as switch): start can be used to start immediately when already programmed to start later. stop will interrupt running program and start cooling phase. An additional stop will interrupt the cooling phase also and completely stop the machine. So states where it makes sense to update switch to off: STATE_WAITING_TO_START (because on will then start), STATE_PAUSED. And to on: STATE_RUNNING (because off will then stop). For all other states it doesn't really matter as trigger will not work.