Turnitin should use Moodle Class Autoaloading

[mhughes2k]

This code from

moodle-plagiarism_turnitin/lib.php

Line 70 in 8cf0d4f

// Include plugin classes.

onwards is anachronistic.

The classes that are being manually loaded have already been physically placed in the relevant location (/classes) for Moodle class autoloading to be performed, but named in a way that is not compliant with this.

There should be no need to come up with an alternate way for PHP classes to be loaded.