[SPARK-1186] : Facilitate configuration for Saprk Mesos Coarse Grain.

Added the `--mesos-coarse` grain flag.

```
    --mesos-coarse       : Enables coarse grained execution in Apache Mesos, this will launch only one long-running
                           Spark task on each Mesos machine, and dynamically schedule its own “mini-tasks” within it.
```

[ticket: SPARK-1186] : Enrich the Spark Shell to support additional arguments.
https://spark-project.atlassian.net/browse/SPARK-1186

Author      : bernardo.gomezpalacio@gmail.com