Bug 1007535 - Add new console command, "ussd unsol", to generate USSD uns...

Please see [bug 1007535](https://bugzilla.mozilla.org/show_bug.cgi?id=1007535).

This patch add a new console command to generate ussd unsolicited response.

```ussd unsol <type> <message_str>```

The possible value of ```type``` as below:
- __0__: no further user action required
- __1__: further user action required
- __2__: USSD terminated bu network
- __3__: other local client has responded
- __4__: operation not supported
- __5__: network time out