Draft: Initial JSON support

Just in a few commands for now for a proof of concept; e.g.:

$ sudo qmicli -d /dev/cdc-wdm1 -p --nas-get-tx-rx-info=lte -J | jq
{
  "result": {
    "error-status": "0",
    "error-code": "0"
  },
  "rx-chain-0-info": {
    "is-radio-tuned": "yes",
    "rx-power": "-832",
    "ecio": "-43",
    "rscp": "-2147483648",
    "rsrp": "-1045",
    "phase": "0"
  },
  "rx-chain-1-info": {
    "is-radio-tuned": "yes",
    "rx-power": "-690",
    "ecio": "-32",
    "rscp": "-2147483648",
    "rsrp": "-891",
    "phase": "0"
  },
  "tx-info": {
    "is-in-traffic": "no",
    "tx-power": "-32768"
  }
}