Support the EG 1.0 spec

[danwallach]

We're currently supporting EG 0.95. We need to:

• enumerate the changes from EG 0.95 to EG 1.0
• support write-ins (hashed ElGamal stream cipher?)

[danwallach]

• Do we need to support overvotes in any way, or are we assuming a front-end UX that forbids overvotes?

[danwallach]

Get started on these: Section 3.3.4: Contest overvote information Section 3.3.5: Contest write-in data

[danwallach]

Section 3.5.3: Decryption of contest extended data (need for testing, but not for production use)

Q: Do we need to worry about Guardian stuff / key sharing / etc.?

[danwallach]

Section 4.1: Election manifest

• work your way through the spec and make sure we're compliant
• eventually, do the same thing for ElGamalCiphertext, the Chaum-Pedersen proofs, etc.
  • you should only have to change the serialization code in json.ts

[danwallach]

The encryption proofs, etc., use names like challenge and response, which are different from the single-letter variable names we use in chaum-pedersen.ts. Don't change anything in chaum-pedersen.ts, instead, just change the serialization stuff in json.ts.