add permissions explanation to role selection section

coldfront/core/project/templates/project/project_user_detail.html

@@ -53,7 +53,13 @@ <h3>Project: {{project.title}}</h3>
           {% else %}
             <tr>
               <th scope="row">Role:</th>
-              <td>{{project_user_update_form.role}}</td>
+              <td>{{project_user_update_form.role}}<br/><br/>
+                <b>Users</b> can view information about their project and the project's related allocations.<br/>
+                <b>Access Managers</b> have the permissions to manage group membership and permissions.<br/>
+                <b>Data Managers</b> have the permissions to make allocation requests.<br/>
+                <b>General Managers</b> have all the permissions of a PI.<br/>
+                <b>PIs</b> have permissions to manage the project and its related allocations, regardless of their assigned projectuser role.<br/>
+              </td>
             </tr>
             <tr>
               <th scope="row">Notifications On:</th>