[DependencyInjection] added support for expressions in the service container
[HttpFoundation] added ExpressionRequestMatcher
added support for expression in control access rules
added a Twig extension to create Expression instances
[ExpressionLanguage] improved performance
[Routing] added support for expression conditions in routes
mades things more consistent for the end user
[Validator] added a constraint that runs an expression
added optimized versions of expressions