Add stage_in() method on pilot.

This allows one to stage (shared) files to the resource the pilot is running
on.
This can either be in the "special" staging area or a regular place on the file
system.
Make use of new stage_in() method.
Use SETTING for use in other places.
Convert single entries into a list for ease.
Catch unknown type.
Use "configurable" location of staging area.
Create staging directory if it doesn't exist yet.
Cleanup examples.
Create output directory in the agent in all cases.
Also support absolute paths for stage_in().
Tune examples.