Add multiple executors

Refactoring / clean up
Adding executors instead of framework messages
We need to pull hdfs-site repeatedly.  The reason why is that the name node may die and a new name node may pop up or a different journal node may appear.  Basically the cluster state may change over time.  So in this executor we repeatedly update the configuration to get the latest configuration.  Also, we need this executor to handle HDFS specific command execution.  We need error handling if a node dies and some nodes require more than one command in a specific sequence.  We are extending the Executor but we need our own custom functionality for our use case.