Change 'target' to 'jobs'

[wandell]

A job can be created that will require multiple PODS (and potentially Nodes). In our code, we refer to a job as a 'target'. ZL and I think that we should rename 'target' to 'job' to be simpler and consistent with the kubernetes notation.

This will take a pleasant hour of screwing around.

[wandell]

also, let's change maxInstances to maxNodes.