Updates for batch processing

[jhennies]

I've updated the batch processing module:

1. save_ij_tiff instead of imsave
2. Open the first image and resulting segmentation in the end to illustrate that the workflow was working
3. Added the suggestion to first only build an empty analyse function and run it to make sure this works before filling in functionality
4. Changed the variable name of the input directory outside of the function

Regarding 3., I'm not sure if this is understandable, any suggestions are welcome.

[tischi]

Awesome thanks @jhennies !