[mythtv] AVInfo based on TSDemux

New object able to parse a MPEG-TS stream.
[mythtv] Private sub-class MythProgramInfo::Props

Intented to store some volatile properties collected by the instance
- Video frame rate
- Video aspec
[mythtv] Enable EDL for MPEG-TS stream

Opening the recorded stream, a demuxer is initialized and parses the stream to discover AV props.
Then if FPS is available we can convert marks "frame count" to time position (ms).