Perform Cleaning module: Option to download flagged data

[tom-gu]

To add an option to also download a flagged-only version of the data (i.e with no filtering).

Plus, we should give the R filtering query, as it will supply a basic level of reproducibility; one that we'll surely improve in the future.

[thiloshon]

Ask @Martis6 if this option is available in bdchecks

[Martis6]

@thiloshon Flagging info is stored in the main output of perform_dc() function, so it's only the matter of extracting it.
Example of 43rd data check: