Added a test forbidding to expand CoreDriver outside the DriverInterface
Added a test forbidding to expand CoreDriver outside the DriverInterface

The goal is to prevent mistakes in contributions where new features are
added in CoreDriver without being added in the interface.

Chekote/Mink,minkphp/Mink,jhedstrom/Mink,jordi12100/Mink,Behat/Mink,jordi12100/Mink,aik099/Mink,Chekote/Mink,minkphp/Mink,jhedstrom/Mink,talib570/Mink,talib570/Mink