Updated phpstan from 0.11.19 to 0.12.19, including a bunch of its dependencies.
Increased level from 7 to 8
Ignored new check for return types, so we do not enforce adding them to all methods (returning void isn't compatible with PHP 7.0 and adding return types on certain public functions does not work in Magento 2.1.x)
voidisn't compatible with PHP 7.0 and adding return types on certain public functions does not work in Magento 2.1.x)