Add cover support

[steinerl]

Hello,

this implementation includes a generic cover class and a specific class for the Fibaro FGRM-222 device to support the "Venetian blind"/tilt mode.

Currently, the decision whether to use the FibaroFGRM222Cover class or not is solely based on the MANUFACTURER_ID and PRODUCT_TYPE. In the future, the decision should also be made based on the configuration (Venetian blind mode active), once the python-openzwave-mqtt library properly supports list values (see cgarwood/python-openzwave-mqtt#53).

A few limitations of this implementation currently:

• Only covers with primary CommandClass SWITCH_MULTILEVEL supported
• SUPPORT_STOP and SUPPORT_STOP_TILT not available - the implementation via the open/close switches (like in the old Z-Wave component) did not work in my tests, so I used the level value instead. Maybe someone else could implement/test this.
• Fibaro FGRM-222 covers will always have tilt support regardless of the configuration

Fixes #9

[marcelveldt]

Thanks for your help! Code looks fine to me, assuming you took the existing hass implementation as example ?

[steinerl]

Yes, I took the existing Z-Wave component as an example, but I only implemented the parts that I was able to test - hence no implementation for the garage door devices.

[marcelveldt]

sounds familiar, I had the same thing when implementing lights support as I only own dimmers and not (rgb) bulbs.

[MartinHjelmare]

I think we can merge this.