Move newgroup page form logic to a backend Perl script and methods.

     www/newgroup.php3 - The reworked PHP page.
     www/newgroup_form.php3 - Removed, form merged into newgroup.php3 .
     www/group_defs.php - Add a Group::Create method bridging to the script via XML.
     www/showproject.php3 - Link to newgroup.php3, rather than newgroup_form.php3 .
     configure configure.in  - Add the newgroup backend script.
     backend/{newgroup,GNUmakefile}.in - Add the Perl script.
     db/Group.pm.in - Update the AccessCheck method to allow TB_PROJECT_LEADGROUP.
     sql/database-fill.sql - Add table_regex 'groups' checking patterns.