Batch processing - Include workflow file in log file

## Use Case
I think it would be useful for the plugin user to have a record of which workflow was used to generate the files in the output directory.

## Solution
Include the name (and path?) of the workflow json file used for the batch processing at the top of the log file. For example:
```
Batch processing run with workflow /Users/nahyung.choi/Documents/Test Files/sec61b_workflow.json

SUCCESS: /Users/nahyung.choi/Documents/Test Files/batch_input/test_sample_single.tiff. Output saved at /Users/nahyung.choi/Documents/Test Files/batch_output/test_sample_single.segmentation.tiff
SUCCESS: /Users/nahyung.choi/Documents/Test Files/batch_input/tutorial-mitochondria_1.ome.tif. Output saved at /Users/nahyung.choi/Documents/Test Files/batch_output/tutorial-mitochondria_1.ome.segmentation.tiff
2/2 files were successfully processed.
```