DDC-510 Move Exception for no Metadata Driver from Configuration to EntityManager::create, commit missing MetadataFilter

DDC-510 - Refactored Metadata Driver to be an required option, even for Annotations - allowing to use the specified paths in ORM Tooling Commands

DDC-502, DDC-507 - Changes to how Annotation Metadata Driver is handled in SchemaTool Command, Specifiying Mapping paths is now required for this to work.

[2.0] DDC-341 - Added Composite Model-Set and 3 tests, fixed two bugs in SqlWalker with Composite Key support

[2.0] DDC-342 - Throw Exception with notice in case of Many To Many relation pointing to Joined Inheritance Hierachy until this feature is completed

[2.0] DDC-341 - Added Composite Model-Set and 3 tests, fixed two bugs in SqlWalker with Composite Key support

[2.0] DDC-484 - Fix reference to Doctrine\ORM\ORMException in ProxyException, added two unit-tests for missing tests of ProxyException throws

[2.0] Fixed and added some missing/wrong docblocks. Renamed Assigned to AssignedGenerator as scheduled to be renamed.