Merge pull request #139 from BnLG/snom

Snom enhancements

Hello,
This PR brings several improvements to the Yealink plugin :

It properly adjusts account details display, replacing useless SIP user ID with the extension number.
It disable local phonebook if remote phonebook is available (so that we're sure it's properly used).
It adjusts retry_after_failed_register, making devices to retry faster on their first retries, as some SIP-TLS configured devices systematically wait 2 minutes before registering. Adjusting retry_after_failed_register like in this PR solves this issue.
It ajusts provisioning_order, allowing to provision Snom devices manually. This modification does not break DHCP provisionning, it simply allows devices to provision manually if they do not receive any provisioning option from DHCP.
It enables SIP-TLS and SRTP on a per-line basis.

Thank you 👍
Before :

After :

Reviewed-by: Alexandre Fournier <None>