closes #334 added a process id to metric keys

The main method classes of oracle and worker extend AbstractTwillRunnable where you can call getContext() to retrieve the instance id:

```java
public class FluoOracleMain extends AbstractTwillRunnable {
  
  @Override
  public void run() {
    int instanceId = getContext().getInstanceId();
  }
}
```

The run() method with an `@Override` is only called by twill.