Check/uncheck dependencies of import data

We already do this in the backend. Friendlier if we do it on the
frontend before the user submits the page.
Remove warning.
Merge pull request #266 from afuna/no-warn-schwartz

Remove warning.
Move "update icons" to a different section for clarity

Also tweaks description / headers.
Merge pull request #264 from afuna/importer-dependency-detection

Adjust the importer frontend: