Feature module Twenga 2.0

Feature module Twenga 2.0
Because your function ```is_ssl()``` is just used at the [line 403](https://github.com/PrestaShop/PrestaShop-modules/pull/337/files#diff-2982582933747b9da8d03461999eefc6R403), you could return directly 'on' and 'off' instead of converting a boolean value.