Execute multiple segmentation algorithms in a single PlantSeg run

[wolny]

It would convenient to execute multiple partitioning algorithms and save the results in a single h5 file, so that one can easily compare the results. We could make that option available only from the config file for now.

[lorenzocerrone]

It would be cool to have a proper schedule-engine for that.. I think that Anna's idea to use Dask could really allow us to do this in a cool way..

But yeah in the short term we could easily have this as an additional process, the only problem will be handling the postprocessing