[2.0] Refactorings in DQL parser to allow more granular enhancements scheduled for later versions. Fixed issues with missing validations of invalid ResultVariable, Unknown query components and Re-declaration of query compoenents.

[2.0][DDC-183] Fixed issue with Annotations parser failing on identifiers that matches with token types.

[2.0] Incorporated CLI refactorings. Added support to namespaces and unlimited depth namespaces. Dropped globalArguments for now, since they interfer in DAG implementation.

[2.0][DDC-206] Fixed wrong enumeration value. Changed XSD location to point to the document on the website.

[2.0][DDC-122][DDC-97][DDC-98][DDC-147] Refactored metadata mapping drivers by removing the useless PRELOAD mode. Introduced ClassMetadataFactory#getAllMetadata. Classloader simplifications. Old classloaders deprecated. New Doctrine\Common\ClassLoader is almost the same as the previous IsolatedClassLoader.

[2.0] DDC-169 - Further refactorings, schema max identifier length is now used for asset generation. Added platform-wide test for unique index generation with create table.

[2.0][DDC-171] Fixed (second attempt). Some other cleanups. Performance fix for mock Statement used in hydration performance tests for more accurate and better results.