[LMS-520] Allow pre- and post-methods for db migration written in Java

.../java/ch/systemsx/cisd/dbmigration/DBMigrationEngine.java

...source/java/ch/systemsx/cisd/dbmigration/IDAOFactory.java

...systemsx/cisd/dbmigration/IJavaMigrationStepExecutor.java

...rce/java/ch/systemsx/cisd/dbmigration/IMigrationStep.java

.../systemsx/cisd/dbmigration/JavaMigrationStepExecutor.java

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

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

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

...temsx/cisd/dbmigration/JavaMigrationStepExecutorTest.java

.../systemsx/cisd/dbmigration/MigrationStepFrom001To002.java

.../systemsx/cisd/dbmigration/MigrationStepFrom002To003.java