Crypto and mapping reviews

- Crypto: Removed DoubleClickCryptoException,
  adopting javax.security's standard exception types;
  fix initVector.timestamp field; provide getters
  for initVector.timestamp and initVector.serverId;
  default initVector uses (timestamp, random) nonce;
  fix block cypher case for >1 blocks; review javadocs,
  Price method names (millis/micros)
- Metadata: Add content-labels, publisher-verticals
- Mapper: Fix AdPosition & Banner.mimes; add Banner.expdir,
  Content.contentrating, User.data.segment (Verticals),
  Video.startdelay (special values)