Allow WorkflowManager to Properly Cache Results

The WorkflowManager caches results from the most recent experiment. If you do this:

``` python
workman.run()
workman.export()
workman.export()
workman.export()
```

... the experiment is only run once. But the Web App always calls `run()` then `export()` (or `output()`), even when the experiment settings are the same.
