Prevent abuse of site trials

Not sure whether the capability exists yet, but I think it will be possible to integrate with drupal.org SSO.

@jdleonard that's a pretty steep barrier to entry that would dissuade many prospective Drupal clients/users from using Forge to test out Drupal.

We are trying out a solution that makes the launch button active when a user is confirmed to be human and replaces the launch button with a link to the trial site so users only run one trial at a time.

@w01f Fair enough. I was riffing off of "Require registration to launch sites" in the issue summary.