Device triggers now functional

Fixed an issue where device triggers were not loaded. Also added error messages in case the DeviceAutomationConfig is invalid.

The option to create triggers via yaml is removed from the readme. When creating device triggers, a device_id is mandatory. This device_id can only be retrieved through the HA device registry, which is coded in the backend, and will be executed when creating automations via the UI.

Again, if there are any issues, we'd love to hear! Enjoy using your Crownstone presence in HA!