Add option to download preprocessed files in batch

[RonnieKrup]

It seems like it is only possible to download the preprocessed files from the 'runs' browser. When searching for specific sessions or subjects, it is currently not possible (or not intuitive?) to download a the preprocessed files for those subjects in batch (as one can for the raw files).
Ideally - either an option to search for specific preprocessed files in the scans browser, or an option to filter the runs based on subject or study properties would help