Working and clean dataset outputs are difficult to review

[cristinamullin]

Is your feature request related to a problem? Please describe.

Users have complained about the total number of columns in the output datasets. Users would like to be able to filter this more easily (generate different views/tabs in the output?) or choose to remove columns they don't want (maybe a list of unique cols could be generated and user could select ones they want to remove?).

Describe the solution you'd like

Consider running TADA_RetainRequired() when producing the "clean" dataset. This will reduce the number of columns.

Also consider related issue: #212

Finally, I think that we could produce a summary output file (maybe a word document) to accompany the dataset outputs that may help with this issue.

Reminders for TADA contributors addressing this issue

New features and/or edits should include the following work:

• Create or edit the code.

• Document all code using line/inline and/or multi-line/block comments
  to describe what is does.

• Create or edit tests in tests/testthat folder to help prevent and/or
  troubleshoot potential future issues.

• If your code edits impact other functionality in the shiny
  app, ensure those are updated as well.

• Run styler::style_pkg(), devtools::document(), and devtools::check()
  and address any new notes or issues before creating a pull request.