Documentation Fix

This fixes some documentation issues.

AdfsReaderHD class added

A new class has been added to read ADFS hardisk images (AdfsReaderHD), it has the same interface as AdfsReader.
None of the interfaces for the other classes have changed.

Small fixes

Fixed some small issues thrown up by phpstan

Initial release

Update DfsReader.php

Removed leading \ from namespace, and added a use line for exception.