EXP-42. Adds a ModelProducer class for running Extract and Score.

Reviewed by: kiyan
EXP-56. Renames RunSpec and ModelSpec.

RunSpec is now ModelEnvironment.
ModelSpec is now ModelDefinition.

Reviewed by: kiyan
EXP-57. Removed references to model pipelines.

Reviewed by: kiyan
EXP-60. Adds ExtractScoreJobBuilder.

Reviewed by: kiyan
EXP-60. Adds back missing comma to fix build.