Better result download predictability by knowing the result compressed size in msgpack.gz format

Implements CLT-202
Reduce table length validation from 256 to 255
Add result_size to Job class

Changes:
- Add result_size, the job's compressed message pack
  size in bytes, to the model
- passing result_size around and exposing it through
  the user facing apis as part of the Job class
- Fixed some tests and added new to cover this
  new feature

Implements the client library side of CLT-202
Fix tests api specs after commit e8ff0b65
Merge branch 'master' into branch 'CLT-202'