Add basic support for ZigDC

[xyzroe]

Add basic support for ZigDC - Zigbee 6ch DC power meter

[xyzroe]

It seems like everything has been fixed. Thank you!

[Koenkk]

Thanks!

Could you also submit a picture for the docs? This can be done by:

1. Create a fork by clicking here
2. Go to the public/images/devices directory, Add file -> Upload files
3. Upload the files and press Commit changes
4. Press Contribute -> Open pull request -> update title/description -> Create pull request

Make sure that:

• The filename is MODEL.png (update model accordingly)
• The size is 512x512
• The background is transparent (use e.g. Adobe remove background)