meta: write device versions to MTS metadata

[Trek Hopton]

We should be writing some important device data to the MTS metadata for media recorded (audio and video).

We should include:

• Device model and version
• av repository version for current build

The PSI time is 2 seconds so this will be included in the MTS every 2 seconds (see variables.go)

See:

• updateMeta() in encoder.go to add/update a descriptor
• ‘meta’ package in container/mts/meta for Encode() and EncodeString()

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