Merge pull request #141 from BnLG/N720

Gigaset N720 enhancements

Hi,
This PR brings some enhancements to Gigaset N720 :

It enables firmware updates. I found a trick to make the firmware link compliant with what N720 expects (it must end with the binary name), while keeping it served by Wazo itself. Look at the links for technical workaround, self explanatory :) Good news is that I'll be able to replicate this for N510 (see #142) 👍
It disables Gigaset.net info/news by default. Privacy is best.
It saves some characters on display name, characters are counted on these DECT screens...
It updates firmware to last version (tested, no issue with standard features).
It properly sets admin password.

Thank you 👍

Reviewed-by: Alexandre Fournier <None>