move schemas into separate directory
various minor cleanups

 * update test_play.tcl script to take url, user, pass as arguments
 * put database credentials into a configuration file
 * put php ini settings into a configuration file
 * minor formatting improvements:
   * change php start tags to <?php
   * remove unnecessary ending php tags
   * indentation fixes
   * print() to print without brackets (in api.php)
 * change api to exit more often rather than nesting clauses
 * remove unnecessary header() use in register/index
 * api: say 'invalid request' rather than nothing if invalid request
 * fix lack of html encoding in header - probably lots of other places