Move original project plan to designs.

[iphydf]

It's slightly outdated now, but it's worth keeping around for reference.

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This change is 

[robinlinden]

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Reviewed 3 of 3 files at r1. Review status: all files reviewed at latest revision, all discussions resolved.

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Comments from Reviewable

[Zer0-One]

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Reviewed 3 of 3 files at r1. Review status: all files reviewed at latest revision, all discussions resolved.

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Comments from Reviewable