[DE] Add support for floors to control covers

[badewanne1234]

The cover domain sentences do not support Floors.

cover_HassGetState.yaml
cover_HassTurnOff.yaml
cover_HassTurnOn.yaml

Everywhere, <area> is used, which only allows to control covers in an area.
If <area_floor> would be used (its already prepared in _common.yaml), one could also control covers in floors and not only areas.

Example from cover_HassTurnOn.yaml:
current:
- <öffnen> (<abdeckung>|<tor>|<garage>) <area>

update:
- <öffnen> (<abdeckung>|<tor>|<garage>) <area_floor>

Would be a nice add-on.
Thank you.