Change IZencoderClient.createJob to return domain object instead of raw server response

[aleksey-korolev]

For convenience of API users it would be nice to have IZencoderClient.createJob return ZencoderJob instead of raw xml Document.
PHP API implementation from zencoder may be used as example.
Raw response (xml document or Json string) may be saved inside ZencoderJob (for example for the case when server response is extended but API implementation is not updated yet).
It is possible to update and return ZencoderJob that was passed to createJob method or construct and fill a new instance.

[drallgood]

Actually a good idea. Don't know when I'll have time for it, though.