Merge pull request #136 from BnLG/d7c

Add Snom UXMC D7C firmware entry

Hello,
This PR adds Snom UXMC D7C firmware entry, making it available through Wazo portal.
https://service.snom.com/display/wiki/D7C
https://service.snom.com/display/wiki/UXM+-+D7C+-+V1.1.1
It also updates the firmware_uxm option in the Snom plugin template, depending on what has been downloaded.
Finally, this PR updates Snom firmware links to HTTPS, as their HTTP links do not respond most of the time.
No issue with HTTPS.
Ref : Wazo ticket #5638.
Thank you 👍

Reviewed-by: Alexandre Fournier <None>
Reviewed-by: BnLG <None>