[2.0] Refactoring some common code in to the AnnotationDriver and creating PhpDriver for consistancy

[2.0][DDC-34] Fixing issue with duplicate association mappings when dealing with mapped super classes

[2.0] Added functionality to convert a Doctrine 1 schema to Doctrine 2 to help users with upgrading. Lots of other small bug fixes and changes.

[2.0] More work on ClassmetadataExporter and ConvertMappingTask for converting mapping information between various formats

[2.0] Some work over SchemaTool update of schema (affects directly the CLI schema-tool task on --update option.

[2.0] Refactored classloader architecture. Renamed ClassLoader => GlobalClassLoader. Introduced IsolatedClassLoader that is suitable for participating in autoload stacks. Added 2 example entity classes to the sandbox with 2 xml mappings and 2 yaml mappings. Simplified sandbox setup.

[2.0] Fixing spacing and adding precision and scale in Annotations driver. Also introduced options item in Annotation and Yaml mapping drivers. Missing XML driver implementation.

[2.0] Work on CLI: Added SchemaToolTask with preliminary support for dropping/creating the database schema. Prepared the sandbox. Adjusted build to include the sandbox.

[2.0] Applied fixes for character casing issues. Simplified inheritance mapping and improved handling of outer joins in Class Table Inheritance.

[2.0] Refined implementation and semantics of the merge and detach operations. General cleanups and API improvements. Added a testcase for detaching/serializing->unserializing->modifying->merging to demonstrate the transparent serialization.