[DependencyInjection] made getXsdValidationBasePath() and getNamespace() methods from DIC Extension class optional
[DependencyInjection] made getXsdValidationBasePath() and getNamespace() methods from DIC Extension class optional

This has been changed so that people that do not use XML for their own extensions do
not need to bother implementing these two methods.

symfony/http-kernel,symfony/HttpKernel