Lookup API to keyserver v2

[adon-at-work]

• The lookup verify API is largely based on https://github.com/yahoo/coname/blob/master/cnclient/client.go. As of now, it assumes the struct is readily decoded.
• VRF and sha3 are refactored and moved into the coname directory

p.s. will rebase before this gets merged.

@andres-erbsen , @daniel-ziegler , @diracdeltas. please see if you can give it a review. thanks

[andres-erbsen]

I checked that

• the constants match my understanding of the protocol; charCodeAt evaluations match my browser's understanding
• e2e.coname.toBits_ and e2e.coname.toBytes_ perform big-bit-endian decoding
• e2e.coname.getRealmByUser_ performs a key-value lookup based on the part after the last @ sign; it is up to the caller to make sure that all domains in the configuration are valid.
• I ignored the commented-out merkle tree code.
• e2e.coname.checkCommitment_ performs the commitment check specified in client.proto, which matches my understanding of the protocol
• e2e.coname.checkQuorum_ and e2e.coname.flattenQuorum_ correspond to the Go counterparts assuming the javascript && and !object mean what they look like they mean (which they did based on my limited experiments).
• e2e.coname.verifyQuorumSignature_ verifies the signature under the specified signature scheme
• e2e.coname.verifyConsensus_ matches the Go counterpart and my understanding of the protocol.

I think @daniel-ziegler is more qualified to check https://github.com/yahoo/end-to-end/blob/feature/treeproof/src/javascript/crypto/e2e/coname/lookup_verify.js#L378 and onwards; I will check in with him and do it myself in case he is not available.

[andres-erbsen]

The realm name check we discussed over email is now present in the Go code: https://github.com/yahoo/coname/pull/34/files#diff-a53cc11e5be81686d4eee400a9d85c86R102. Please incorporate it to the JS version as well.

[adon-at-work]

Thanks @andres-erbsen. I'll let you or @daniel-ziegler to check the rest of it (line 378 and onwards). I prefer to leave this PR as is, and will incorporate the realm name check in a separate PR, which I expect to also have all protobuf and the whole ajax request ready. Gotta rewrite some of the code due to the 32 vs 64 bit issue due to the JS protobuf.

[adon-at-work]

merging for now. we'll need another review on the complete lookup client. thanks @andres-erbsen

[adon-at-work]

reversed the merge from master. will merge again with the changes rebased. see https://github.com/yahoo/end-to-end/issues/65 for details