Introduce a mode for the temperature controller

[pLeminoq]

A mode differs from a service that it is more like a strategy and not like a status. The mode should probably contain the following values (oriented towards the according trait from google):

• off: do nothing
• heating: make it warmer
• cooling: make it cooler
• heatcooling: keep the temperature in a specified range

When this is implemented the cloud connector has to be adapted accordingly.