revid: remove input specific parameters from config

[Saxon Milton]

With the addition of more and more different input devices, revid is becoming more complicated with configuration and it’s validation.

I propose that we remove input specific parameters from the revid config. Input options can be dealt with the input selected. We should have the revid ‘constructor’ take function options, one of them being a function to select the input device. For example,

revid, err := New(
  Input(
    picam.New(
      Codec("H264"),
      Bitrate(40000),
      Brightness(50),
      ...
    )
  ),
  ...
)

In doing this, we can simplify the revid API and make configuration less complicated.