add constructor that doesnt mess with datastore keys

[whyrusleeping]

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[whyrusleeping]

I kept getting when putting '"/blocks/CIQCBILJFHXDYSZJ5TQRRQ4SN3EH4AW4MF2CLK4O5QGU3QZX5LAAIEA"': key not supported by flatfs and couldnt figure out the right incantation to get it working.

In any case, this seems like a good thing to have.

[Stebalien]

Yep. The main issue is that flatfs doesn't encode keys (just restricts the keys). Ideally, we'd have a flatfs2 that actually handles key encoding.