Doesn't take into account users with 'administer nodes' permission

Users with in a role with the 'administer nodes' permission can create content of all types whether they have create permission for that node type or not. They also may not belong to a role that's given any create permissions.

Because _preferred_format_get_available_node_types only checks for create [node-type] permissions such users will not see all (or possibly even any) of the content types they can select their preferred filter for.

Patch attached adds a check for the 'administer nodes' perm.