Member properties of parameter $configuration of class Configuraiton are overwritten in method configureMigrations in class DoctrineCommand (Issue #81)

Bugfix of an old problem, which had not been fixed by a pull request yet.
Member properties of parameter $configuration of class Configuraiton are overwritten in method configureMigrations in class DoctrineCommand (Issue #81):
If someone explicitly uses the command line option --configuration along the doctrine:migrations:generate or doctrine:migrations:migrate commands to set a separate configuration file (e.g. a yaml-file with entries: name, migrations_namespace, table_name, migrations_directory), then it is correctly loaded by method load of class AbstractFileConfiguration and in turn read e.g. by the method doLoad of class YamlConfiguration from the yaml-file.
In method configureMigrations(ContainerInterface $container, Configuration $configuration) in class DoctrineCommand, however, these loaded configuration setting stored in the member properties of the parameter $configuration of class Configuration are set anew with the configuration settings in the app/config/config.yml file (with entries: dir_name, namespace, name, table_name).
The overwriting happens because there is no check whether the parameter $configuration already has set the member properties with a separate configuration file.
To me this appears to be a false implementation and should be fixed.