Implement Switching TV Inputs

[bfayers]

I am creating this issue in favor of my previous issue, #12, since this request includes both apps and input switching since the method used is similar.

I have found example code, albeit in nodejs, for either switching to an app or an input source.

Switching source/app: https://github.com/g30r93g/homebridge-panasonic/blob/master/index.js#L232

HTTP Captures and a method of getting the list of apps can be found in the, now closed, issue #12

[bfayers]

After having a look through the library, it would seem that the library already contains support for launching apps; however it would be preferable that it can generate the app list itself from the TV. as well as switch inputs (See #40 )

[bfayers]

Inputs can be switched via rc.send_key("NRC_HDMI1-ONOFF")