NethVoice: enable websocket transport

[Stell0]

Enable websocket transport for extension on NethVoice 8

• NS8 should assign a port
• Open the WSS port on firewall
• Use the port for WSS transport
• Let Asterisk use the certificate for WSS
• Make sure chan_pjsip is used for WSS

[Stell0]

Test case:

• make sure external address is configured on sip general options on freepbx
• create an extension that uses wss transport
  • remove proxy for the extension
  • transport 0.0.0.0-wss
  • avpf yes
  • icesupport yes
  • rtcp_mux yes
  • media_encryption dtls
  • Enable WebRTC defaults
• check that a phone that uses that extension connected on ASTERISK_WSS_PORT works
• check also after backup restore or move on another node

[Amygos]

Testing release nethesis/ns8-nethvoice 1.4.5-testing.2

[Stell0]

Known issue: seems to have problems to work behind NAT, manually tweaking ICE and STUN may be needed