Invalid Device - Add/State Change

[xenolightning]

Invalid devices are ignored during an "Add".

This may cause the Api to fail to further detect the device.

Possible solutions:

• Attempt to add the device (if it doesn't exist) on every system change event
• Add the devices in an invalid state, and mark them as invalid so they can be filtered out of queries

[xenolightning]

System events will now check for existence of the device, and add the device to the cache if necessary.

This should fix the "lazy" state changes of devices.

This approach was chosen, as it has less surface impact to the controller and device classes.