av/device/device.go now contains the AVDevice interface and implementations of this
interface, namely, raspivid, geovision, webcam and file are contained in the packages
av/device/raspivid, av/device/geovision, av/device/webcam and av/device/file
respctively. config.go and testing was also moved to a new package called config.go in
order to remove would be circular dependency between AVDevice implementations and revid.
Modifications were made elsewhere expecting config.Config to be part of the revid package.
Use http instead of https in gvctrl getLogin request. Gave RTP client a close method so that the conn can
be closed after we're done with the client. Put timeout on reading from the RTP client PacketConn so that
we don't hang on the ReadFrom call if the conn is closed. Closing the RTSP and RTP clients when
startRTSPCamera is returned.
Added required new params to config structure, and therefore also added new defaults and validation checking.
Also updated revid's update func so that we can control new parameters using vars. Now using gvctrl in
startRTSPCamera function and interpreting revid config to configure camera.
Saxon