Feature Idea - get and set panid in gateway

It might be convenient to be able to get/set the panid for an attached xbee right in the gateway.

Here's how it might work:

Getting the panid:

$ gateway --getpanid
Querying xbee...
1234

Setting the panid:

$ gateway --setpanid 8888
Querying xbee...
8888

TODO: describe more about this.