Simplifying Android attestation

On the PR for issue #1, JeffH asked why I was declaring the attestation statement as type any in the top-level IDL. This is an excellent question, and befits a more detailed response than I could give on the PR discussion thread.

As I mentioned in my response, I am wondering if we could eliminate a bunch of client-side processing that consists simply of bit-fiddling the Android attestation to get it into a "pretty" format. To give people a more concrete idea of what I mean, I have attached a version of the "merged" spec (i.e. incorporating the PR changes for both #1 and #61) that eliminates this bit-fiddling. I'd be happy to add this to the PR for #1 if people think it's better than what we have now.

Note that all the differences are in section 4.4.

Thanks,

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-Vijay