Enable users to submit corrections to their submissions

[KMJ1618]

When submitting drug sets or gene sets, mistakes can occur due to submitters' errors (e.g. typos) that the submitter doesn't realize until after submission has occurred. The platform doesn't currently provide a way for submitters to report a problem with a dataset they've submitted. It would be very helpful to add a lightweight strategy that permits users to easily report an issue with their submission, as this will facilitate accuracy of the data. Various options are possible; the most convenient would be to have a free-text input box visible on the main submission page with the header "Question? Suggestion? Made a mistake with your submission? Contact us here:" and a Submit button below the box.

Reporting problems with data submissions isn't appropriate for the GitHub issue reporting option that is provided at the bottom of the site's page, so it would be useful to add this functionality.