Add processed spatial data aggregation and quality metrics

[LouisK92]

Some todos:

• Update the generation of the test data as the aggregated processed spatial data is needed

[LouisK92]

Points to clarify:

• How to merge the results from the quality metrics with the results of the metrics?
• In this context. Maybe no problem, but think about: How to handle the case that for the similarity metrics we have control methods expr_corr_and_control_ch = expr_corr_ch.mix(control_ch) which wouldn't be the case for the quality metrics. (Currently quality metrics also don't need control methods imo, but could be that we need some additional control methods in the future)
• How to write the output output_agg_spatial_data generated in the agg_spatial_data_ch to the final workflow output directory? And how to introduce a flag to make this optional (for large runs we don't want to generate endless of large files)

[lazappi]

I think you want to mix in the quality_metrics_ch here. Something like (approximate syntax):

Suggested change

	// Add quality metrics
	.mix(quality_metrics_ch)

This would create add the quality metrics into the channel in no particular order, the post processing can then be applied to all of the metric outputs.

Alternatively (or if this doesn't work), you could add the post-processing blocks to the quality_metrics_ch and then mix the two channels at the end when creating output_ch. This means repeating a bunch of code though.