Added source_dir and target_dir parameters allowing copy of databases outside...

Added source_dir and target_dir parameters allowing copy of databases outside the MySQL default internal directory on Sanger machines /mysql/data_3306/databases/. When target_dir is specified, the script will automatically create a symlink from target_dir to /mysql/data_3306/databases/. This change will allow us to copy databases from and to the new ens-staging3 MySQL server