Temporary directory support for all stages in the pipeline

[thomaswilliamsastro]

I've seen good speed ups doing imaging on a temporary (local) directory with the chunked imaging handler (vs running natively from a NAS system). It would be good to have this feature for the various other stages in the pipeline, to remove the I/O bottleneck. e.g., you could imagine you want to do the postprocessing on a local SSD, but keep an entire projects on some other HDD

[thomaswilliamsastro]

Note it seems like this isn't just useful for speed considerations -- if you're running multiple CASA instances on different machines but operating in the same directory, stuff can just hang. This seems horrible