Improvements to the local testing setup

[jbusecke]

• Set up a separate 'local_hub' config that directs all output to a central place
  • Cache should be one central prefix on leap-scratch
  • The output needs some special explanation
• What is needed for production:
  • Reroute only the final target folder to a standardized location.
  • ...
• Can we cache/write out to temp directories locally?
• How do we avoid the final copy stage during local execution? Over at https://github.com/leap-stc/ww3_feedstock the local recipe now executes, but fails at the copy stage due to permission reasons.
  • We could just explain to copy out the stage, but that seems messy...meh maybe that is ok