Implement a command line STUN client software for testing

[bennylp]

Implement command line STUN client software for testing the client side implementation and to test a STUN server as well.

Some functionalities in the client:

• Ability to send these STUN requests and interpret the response:
  • STUN Binding request
  • STUN/TURN Allocate request
  • STUN/TURN Set Active Destination request
  • STUN/TURN Connect request
• Ability to send and receive these indications:
  • STUN/TURN Send indication.
  • STUN/TURN Data indication.
  • STUN/TURN Connect Status indication
• Ability to add credential (short and long term) to all outgoing messages.
• Ability to add fingerprint to all outgoing messages.
• Ability to add other optional attributes in outgoing requests.

Currently STUN Shared Secret request is not supported since this requires TLS connection to the server. It may be supported in the future.

[bennylp]

Done, except TCP related features (Connect request and Connect Status Indication) are not implemented yet.