Energy support and bugfixes

• Stick: Add new properties energy_consumption_today counter and energy_consumption_today_last_reset timestamp. These properties
  can be used to properly measure the used energy. Very useful for the 'Energy' capabilities introduced in Home Assistant 2021.8.
• Stick: Synchronize clock of all plugwise devices once a day
• Stick: Reduced local clock drift from 30 to 5 seconds
• Stick: Optimized retrieval and handling of energy history
• Smile: add the required sensor attributes for Energy support
• Smile: add last_reset timestamps for interval-sensors and cumulative sensors
• Smile: fix the unit_of_measurement of electrical-cumulative-sensors (Wh --> kWh)