[WIP] Add away mode support for generic thermostat

[fanthos]

Description:

Pull request in home-assistant.github.io with documentation (if applicable): home-assistant/home-assistant.io#4202

Example entry for configuration.yaml (if applicable):

climate:
  - platform: generic_thermostat
    name: Study
    heater: switch.study_heater
    target_sensor: sensor.study_temperature
    away_temp_cool: 14
    away_temp_heat: 34

Checklist:

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated in home-assistant.github.io

If the code communicates with devices, web services, or third-party tools:

• Local tests with tox run successfully. Your PR cannot be merged unless tests pass

[fanthos]

Not sure if I need to call the function in turn_away_mode_on and turn_away_mode_on or not.
self.schedule_update_ha_state()

I am confused about difference between
schedule_update_ha_state()
async_schedule_update_ha_state()
yield from self.async_update_ha_state()

Another problem, away mode does not restore after server restart.

[ciotlosm]

Would be nice if you could also allow an option to link this directly to an entity providing home / away status. Most people group all device trackers under a "Presence" or "Family", so that could be used as trigger automatically without extra automation.

Unsure if it's realistic, but would make the component even more useful with default config only.

[ciotlosm]

I've done a few more fixes and integrated part of your changes in this PR #11325
I will update documentation once people decide the pull request is ok considering I have some breaking changes to functionality on the way states are represented and one startup setting.

[Danielhiversen]

@fanthos @ciotlosm :
Is this pr still relevant? Or should we close it?

[fanthos]

I think this feature already included in #11445 .