Templates instead of entity state on light cards

[lukyjay]

I love the light card but the entity state is not very useful, since we have a coloured icon and brightness slider which shows the entity is 'on'.

It would be great if we could re-use this space with templates.

If we could use templates, I could refer to another entity's state to show whether the light is 'on' because of motion/occupancy sensor, or if it was manually toggled on.

Here is what it could look like:

This idea could also apply to other cards with the 'show state' option.

[capandcamera]

An idea of how to implement this one: Leave State as-is and have that as the expected behaviour, but if show_state is false, then allow another toggle of show_label

That label if enabled would allow templates

[KTibow]

Duplicate of #144.