Add proto definitions for (AES) KeyVersion.

Also removing placeholders, since now we have a complete set of code, tests and protos.
I think I made a blunder here; the IV shouldn't be stored. I'll remove this
in the next pull request.

On Saturday, July 5, 2014, Shawn Willden <notifications@github.com> wrote:

> In protos/aes_key_version_proto.proto:
>
> > +package com.google.k2crypto.keyversions;
> > +
> > +message AesKeyVersionData {
> > +  extend KeyVersionData {
> > +    required AesKeyVersionData keyVersion = 10001;
> > +  }
> > +  // Non-core fields go here
> > +}
> > +
> > +message AesKeyVersionCore {
> > +  extend KeyVersionCore {
> > +    required AesKeyVersionCore keyVersion = 10001;
> > +  }
> > +  // Core fields will be hashed into the KeyVersion ID
> > +  optional bytes matter = 1;
> > +  optional bytes iv = 2;
>
> What is this IV for?
>
> —
> Reply to this email directly or view it on GitHub
> <https://github.com/google/K2/pull/20/files#r14572341>.
>