For a more consistent API, completely replace Email API with the Builder. Add support for InternetAddress.

[bbottema]

Email's API and the EmailBuilder API are more or less the same, resulting in a lot of duplicate state / synchronization code, while not adding much in terms of usability.

To keep de code base concise and the API consistent and simple, make Email completely immutable as a build result from the EmailBuilder.

[bbottema]

Merged EmailBuilder-rewrite into master.