Update method signature to use interface instead of class
Update method signature to use interface instead of class

Closes #303

rschumacher/SonataDoctrineORMAdminBundle,pulzarraider/SonataDoctrineORMAdminBundle,nlzet/SonataDoctrineORMAdminBundle,aurelien-vtech/SonataDoctrineORMAdminBundle,sonata-project/SonataDoctrineORMAdminBundle,rmzamora/SonataDoctrineORMAdminBundle,rschumacher/SonataDoctrineORMAdminBundle,rschumacher/SonataDoctrineORMAdminBundle,nlzet/SonataDoctrineORMAdminBundle,nlzet/SonataDoctrineORMAdminBundle,rschumacher/SonataDoctrineORMAdminBundle,pulzarraider/SonataDoctrineORMAdminBundle,rmzamora/SonataDoctrineORMAdminBundle,aurelien-vtech/SonataDoctrineORMAdminBundle,pulzarraider/SonataDoctrineORMAdminBundle,aurelien-vtech/SonataDoctrineORMAdminBundle,rmzamora/SonataDoctrineORMAdminBundle,nlzet/SonataDoctrineORMAdminBundle