Add presence management

Presence management is now available. You should configure a presence sensor (True is someone is present else False) on the last page off the integration.

When the presence sensor switch to Off, the thermostat automatically switch to the 'Away' preset (and corresponding temperature). The current preset is backed off to be restored when the presence sensor switch to on.

Note: the optionnal offset field should not be used because it will be removed in the next release.