monitor valve wiring, battery protection, SDK upate

• permanent deep sleep after low battery detection and reporting (feature)
• capacitor valve driver (feature):
  • monitor valve control voltage to detect wiring errors (e.g. valve not connected, connector corroded, etc.) and to reduce operating time
  • disable remote valve operation after detecting valve operation error
  • report valve operation error via mode property in server request
  • max. valve resistance configurable via server reply
• based on Espressif SDK 2.2.1 (feature)

powersaving & H-bridge driver

The firmware has been reworked for

• improved powersaving
• alternatively supporting a H-bridge solenoid valve driver

and contains several other enhancements and fixes (see for details).