[WIP] Adding class mockup for the scope access simulator responsible of triggering fatal errors

This PR aims at extracting the logic that is currently dumped into proxy objects and move it into an "access simulator" object that applies scope accessibility checks to the executed operations.

The final idea is to be able to reduce the complexity of the code in the current [`PublicScopeSimulator`](https://github.com/Ocramius/ProxyManager/blob/10055319f9dea788f39802bf612358f573b48be1/src/ProxyManager/ProxyGenerator/Util/PublicScopeSimulator.php)