Update autoloader to allow module classes in top-level namespaces

This change updates the auto-loader to allow modules classes to be in their own top level namespaces.

For example, the class `Intern\Command\ShowAddInternship` is in the namespace `Intern\Command\`. The class files resides in `mod/intern/class/Command/ShowAddInternship.php`.

This change modifies the way the way the file path is constructed in order to remove the `Intern\` from the namepsace path, so that the correct file path is generated.

Please test against other modules, because I can't promise this doesn't break other things.