Enable LVFS support for firmware updates

[johnsonm]

LVFS supports DFU and is being used to update a lot of hardware, and is open source and free to host on.

I think it is as simple as writing an XML file with IDs, packing it with the firmware into a .cab file, and uploading it.

[hughsie]

If you want a (free!) account on the LVFS, please email me with this info: https://lvfs.readthedocs.io/en/latest/apply.html -- Thanks!