Provide a way to caclulate audio length, and expose to Tika

[Gagravarr]

Currently, we don't provide any way to work out how long (in seconds) any of the audio streams are

It would be good to provide some support, likely based on paging through the audio frames, for calculating the play length of an audio stream. Once that's available, we should have the Tika parsers add that to the metadata

[Gagravarr]

Implemented based on granules, sampling rates and a new common interface