Kepler

I suggested in bug 3558 that Kepler should create a directory on the user's system for each workflow run and store the trace(s) of the run there along with other files produced during the run.

To make use of this facility easy for actor developers, we could provide an API for easily creating output files (e.g., graphics files containing plots of data) in this location (or copying them from temporary directories elsewhere) and ensuring that such files are named uniquely in that directory.

Note that while the default implementation could leave these run directories on the user's machine, an alternative implementation could transfer data files created during a run from these directories to some other data store, load the trace files into a DBMS to make them queryable, etc.