Allow to add more than one IAX modem from web interface
At the moment, is allowed to assign only one IAX modem from web interface.
When configuring fax server, from web interface it's allowed to select only one IAX modem. To use more than one IAX modem, the user needs to follow this documentation: dev.nethserver.org/projects/nethserver/wiki/Nethserver-iaxmodem
The procedure isn't very simple and involve using shell and manually modifying files.
It would be better to allow to add more modems from web interface, because usually who uses IAX modems for fax, create at least two devices (one for receiving and one for sending) but even more than two