Add version and system filtering and water heater platform

[LavermanJJ]

• Enforce version filtering, i.e. only add entities to the registry which are supported by the API
• Only add entities to the registry which are supported by the system (heat pump / biomass boiler)
• Add water heater entity fixes #30

New Entities:

• X35 buffer for therminator
• External X35, X36, X44 buffer sensors (disabled by default)
• Setting target room temperature (pre work for supporting climate platform)

[LavermanJJ]

fixes #43