Add project selector to "1st page" of the node/add/project-release form

Inspired and emboldened by what I learned over at http://drupal.org/node/199138 removing the evil multipage form for project_issues, we should do the same thing for release nodes.

Instead of converting the release node form into a true multipage form, all we need to do is stick a simple form directly at node/add/project-release with a project selector (restricted to the projects the current user has permission to create release nodes for), and then redirect to the full URL.