added logging for run and load outputs + added Cassandra benchmarking ex...

-Added logging for run and load benchmark outputs
-Added Cassandra benchmarking example blueprint
-Added flags for Config Keys
This joining and splitting of hostnames is confusing. Perhaps keep the hostnames in a `List<String>` attribute all the time, based on the values from the `ConfigKey<List<String>>` or `ConfigKey<String>` as appropriate. Have two methods `List<String> getHostnameList()` whose job it is to retrieve and filter the hostnames and `String getHostnameString(List<String> hostnameList)` whose job it is to combine the hostnames into a form suitable for use on the command line.