Merge pull request #52 in FS/freeswitch from ~DDRAGIC/freeswitch:gsmopen_feature_additions to master

* commit 'a9b2e061':
  mod_gsmopen: clean up "gsm list" output a little
  mod_gsmopen: convert reported RSSI from AT+CSQ to dBm.
  mod_gsmopen: get device manufacturer, model and firmware version info.
  mod_gsmopen: add support for reading own number from ON phonebook using AT+CNUM
  mod_gsmopen: add AT+COPS support to get operator name.