extend manifest processing for audio rules

[mattgarrish]

Here's a start on extending the manifest processing algorithms. It will need to be updated depending on how the various issues I've opened are resolved. (I promise no more now! :)

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Preview | Diff

[iherman]

"Genreating" -> "Generating" (in the manifest processing steps right at the start in the title)

[iherman]

Technically speaking, I am fine with the changes. (Although I still have to implement these to see they work well)

However... I am a little bit concerned that we are much stricter for audiobooks than for the general manifest, which looks like setting the bar for an audiobook fairly high (although they are all validation errors). I hope we are fine with that...

[mattgarrish]

I am a little bit concerned that we are much stricter for audiobooks than for the general manifest

Right, that's what I raised a bit of here: #30 (comment)

Those are the most problematic recommended items I see, but even still there's arguably a number of other properties that aren't warning worthy for every audiobook.

[wareid]

I'm ok with audiobooks processing being stricter, mainly because the format has limitations we've defined in the spec and I don't think we're being unnecessarily strict with holding to those in processing. I'll merge so the masses can read too :).