Add support for smart plugs

[thomluther]

The new smart plugs are announced.
New system exports with installed smart plugs are required to understand which data they deliver through the cloud and what capabilities exist for the plugs.
Anker Smart Plugs

[thomluther]

Beside required full system exports with installed smart plugs showing power consumptions, exports for following conditions are required:

• Power Usage mode is set to Smart Plugs
• Smart Plugs have defined schedule and or delayed toggle (Not clear if this is included in actual system_export data)

[thomluther]

Exploration of various endpoints by smart plug owners is required to verify if following is possible via the cloud Api:

• Query the switch state of a smart plug (most important)
• Change the switch state of a smart plug (equally important)
• Query (and change) the schedule of a smart plug
• Change the tag / label of a smart plug

[thomluther]

Note: The smart plug consumption can be supported probably only when added to a power system such as created for solarbanks.
Stand alone Plugs probably do not send their consumption data permanently to the cloud api. They may however provide their state to the cloud when it was changed? This has to be explored by owners which endpoints can be used to query and change their state.
See also #107