Kepler

The workflow run engine embeds a kepler at workflowrunengine/kepler. Now the workflow run engine runs the kepler by calling the API of the kepler.

I found an issue that if we start another kepler GUI in another location, e.g. ~/project/kepler, the kepler gui will nuke the ~/.kepler/cache directory even though they are in the same suite. This may cause a problem to run the workflow run engine. However, if we start the kepler gui from workflowrunengine/kepler, the kepler gui wouldn't nuke the cache directory generated by the run engine.