Uploadable: Adding support for ODM.

This extension is seriously in need of TestCases for ODM, but with this commits it worked perfectly anyway.

Merged "ClassMetadata" with "ClassMetadataInfo", see https://github.com/doctrine/doctrine2/blob/master/lib/Doctrine/ORM/Mapping/ClassMetadata.php:
```
namespace Doctrine\ORM\Mapping;

/**
 * {@inheritDoc}
 *
 * @todo remove or rename ClassMetadataInfo to ClassMetadata
 */
class ClassMetadata extends ClassMetadataInfo
{
}
```