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

 GNUmakefile.in configure configure.in  - Add the testbed/backend directory.
 www/moduserinfo.php3 - The reworked PHP page.
 www/user_defs.php - Add a ModUserInfo method bridging to the script via XML,
     and remove the ChangeProfile method that is being replaced.
 backend/{moduserinfo,GNUmakefile}.in - Add the Perl script.
 db/User.pm.in - Add a ModUserInfo worker class method for script arg checking.
     Also SetUserInterface, SetWindowsPassword, and AccessCheck methods,
     and a copy of the escapeshellarg fn.
 sql/database-fill.sql - Add some to the table_regex 'users' checking patterns.

Support stuff:
 account/tbacct.in - Update the UpdateWindowsPassword() function.
 db/libdb.pm.in - Add TBDB_USER_INTERFACE_EMULAB and TBDB_USER_INTERFACE_PLAB().
 tbsetup/libtestbed.pm.in - Add TB*EMAIL, TBMAIL_* vars (OPS, WWW, AUDIT).