CDO post-processing job added

A general CDO post-processing job is added that runs CDO commands based on a config. Supported features:

• Run general CDO command with an arbitrary operator and arbitrary arguments.
• Support for operator chaining (implicit and explicit).
• Single statement for splitting all output files per variable.
• Support for retrieving output file name form input file name.
• Input files can also be variable(s) selected from other file(s) (implicit operator chaining).

Closes #16.