WAZO-1713: fix aastra default values

Reviewed-by: https://github.com/apps/wazo-zuul

reason: using port 0 by default is not a valid value and will make the
phone unusable.

WAZO-1706: fix Aastra/Mitel firmware links

Reviewed-by: Francois Blackburn
             https://github.com/fblackburn1

[WAZO-1324] Yealink W80B - reworked

reason: the way SIP lines are defined changed. It is now necessary to
generate a line template and set the template ID on the line. I tried to
make it so you can have multiple SIP proxies, with different template
IDs generated for each one.

xivo-snom: add MAC in firmware URL

Reviewed-by: https://github.com/apps/wazo-zuul

reason: snom720 does not send MAC in HTTP headers, making the firmware
file request look like an unknown device to provd.

Add Aastra 68xxi 5.0.0 plugin

Reviewed-by: https://github.com/apps/wazo-zuul

xivo-aastra: remove 2.6.0.2019

Reviewed-by: https://github.com/apps/wazo-zuul

reason: impossible to find the firmware anymore

dhcp: fix Cisco 7937G line

Reviewed-by: https://github.com/apps/wazo-zuul

WAZO-1446: fix NAT for Yealink phones

Reviewed-by: https://github.com/apps/wazo-zuul

reason: keep-alives were not sent.

WAZO-1233: fix language files for Yealink v84

Reviewed-by: https://github.com/apps/wazo-zuul