Updated RepositoryClass::class syntax and added an Interface
Updated RepositoryClass::class syntax and added an Interface

In ``getRepository()`` method changed string literal to ``RepositoryClass::class`` name constant.
Also added a couple of missing semicolons.
And to enforce common interfaces for repositories, introduced a stub for ``BlogPostRepositoryInterface`` interface to be implemented by ORM and ODM Repository classes.

alcaeus/mongodb-odm,alcaeus/mongodb-odm,malarzm/mongodb-odm,doctrine/mongodb-odm,malarzm/mongodb-odm,doctrine/mongodb-odm