Extract audio type from TS descriptors

[jan-varecka-signageos-io]

The audio type of the stream, as defined by ISO/IEC 13818-1 in section 2.6.18, can be mapped to RoleFlags. Then this information can be used by the user for better selection of audio stream.

Real UC: source contains two audio streams, both are in the same language. One of them is intended for visually impaired viewer. With information about audio type, the user can better decide which stream he wants to hear.

As audio type can be mapped to RoleFlags, I have decided not to extends Format class.

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[rohitjoins]

Have moved the AudioType interface from C to TsUtil as this information is only related to TS files.

I'm going to send this for internal review now. You may see some more commits being added as I make changes in response to review feedback. Please refrain from pushing any more substantive changes as it will complicate the internal review - thanks!