Add explanations to drift alignment tutorials section of Help.  Fixes #720
Add explanations to drift alignment tutorials section of Help.  Fixes #720

OpenPHDGuiding/phd2,OpenPHDGuiding/phd2,OpenPHDGuiding/phd2,OpenPHDGuiding/phd2,OpenPHDGuiding/phd2,OpenPHDGuiding/phd2