Add new task parameter -- post_process

[banerjek]

After jobs complete, it's often necessary to perform auxiliary processes such as object file manipulation or map copying/modification (useful with multisystem implementations)

Suggest new task parameter "post_process" which is a system call to whatever is passed to it (string of shell commands, path to script/program, etc)

[bltravis]

@banerjek Are you thinking this is defined in the task definition?

[banerjek]

Yes, exactly