Move newimageid page form logic to a backend Perl script.

     www/newimageid.php3 - The reworked PHP page.
     www/imageid_defs.php - Add an Image::NewImageId class method
                            bridging to the script via XML.
     backend/{newimageid,GNUmakefile}.in configure configure.in - New backend script.
     db/Image.pm.in - Add a Create class method for script arg checking.
     sql/database-fill.sql - Add to the table_regex 'images' checking patterns.