Change wrapper css class for more private function 
Change wrapper css class for more private function 

I think write css class `wrapper` for this plugin sometimes will conflict with anthoer css class (even when using Nested CSS with `.dropdown-content`), in many themes/layout/framework `wrapper` class ussualy use in their template.
execut/yii2-dropdown-content-input,execut/yii2-dropdown-content-input