Support AT -> SR conversion

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The conversion of AudioTrips format to SynthRiders in a target to allow a better inter-community distribution as well as companionship when developing custom songs.

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A rough skeleton with core functionality was implemented in b108339:

• Rough implementation for AT -> SR conversion (Metadata and function headers)
• Moved conversion types into submodules

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• Fixed Switcheroo of library files: 42cfc29
• Simplified entrypoint by using Duck-Typing: 2d8a51e