• UI: improve video aspect ratio handling. Live streams formerly worked
  around a Firefox pixel aspect ratio bug by forcing all videos to 16:9, which
  dramatically distorted 9:16 camera views. Playback didn't have the same
  workaround, so anamorphic videos looked correct on Chrome but slightly
  stretched on Firefox. Now both live streams and playback are fully correct
  on all browsers.
• UI: better error messages on live view when browser is unsupported,
  sub stream is unconfigured, or sub stream is not set to record.
• upgrade to retina v0.1.0, which uses SET_PARAMETERS rather than
  GET_PARAMETERS as a RTSP keepalive. GW Security cameras would ignored
  the latter, causing Moonfire NVR to drop the connection every minute.