[2.0] Refactoring code for reading multiple sources of mapping information from ClassMetadataExporter to a new ClassMetadataReader tool so it can be used to read mapping information easily from multiple different sources. This is used for generating repositories, converting mapping information, generating entity stubs, etc. Generally though, it is useful to be able to read the information for some mapping files into an array of ClassMetadataInfo instances without it being bound to the ORM and the metadata referenced by the EntityManager ClassMetadataFactory