Download Monitor - Google Drive 4.1.0

* Fixed: Files from shared drive can now be downloaded.
* Fixed: Compatibility with Download Monitor 4.6.0
* Changed: Notices priority set to 8.
* Fixed: Fix for PHP 5.6 error "unexpected '::' (T_PAAMAYIM_NEKUDOTAYIM)".
* Added: PHP requirement, at least 7.1

* Fixed: Check if class exists on extending it
* Fixed: Sanitization on option saving

Tweak: Made plugin compatible with Download Monitor 4.0
Tweak: Replaced custom autoloader with Composer class map.