add: support for Java migration steps who need the DatabaseConfigurationContext

...ce/java/ch/systemsx/cisd/dbmigration/h2/H2DAOFactory.java

...systemsx/cisd/dbmigration/java/MigrationStepExecutor.java

...msx/cisd/dbmigration/postgresql/PostgreSQLDAOFactory.java

...a/ch/systemsx/cisd/dbmigration/DBMigrationEngineTest.java

...emsx/cisd/dbmigration/java/MigrationStepExecutorTest.java

...emsx/cisd/dbmigration/java/MigrationStepFrom002To003.java