Update my own comments in silverstripe-comments

The idea is to be able to update your own comments without requiring an admin to do it.

  • You can only update your own comments
  • You need to be uniquely identified (by login)

Context: We are using silverstripe for https://extensions.libreoffice.org/ one of our users suggested to be able to edit their own comments and reviews in the page. The need to change a review it’s also important for us since new versions of an extension can change the review.

Related: I have one PR in progress