Separate CSV files exported for each mask

[paulmueller]

Sometimes (especially in older measurements), we didn't save individual files for the repetitions during the acquisition. Impose currently extracts mask-based values in the same table in the same csv file and labels it correctly, so we can assign maps/timepoints later on. Would it be also possible to save the extracted data in separate files instead of the same table. So one csv file results from one mask detail from one map, and not from one mask details from multiple/consecutive maps.