Project registration page should prominently state how to request a project group

Only Launchpad admins can create project groups. The project registration page gives, toward the bottom, a description of what a project group is but the page doesn't explain how project groups are created.

We should have a prominent notice above the fold on this page stating:

"If your project is part of a larger group of projects, and you want to reflect that in Launchpad, please do not attempt to register that project group here. Instead, <a href="https://help.launchpad.net/Feedback">contact us</a>."