SPARK-938 - Openstack Swift object storage support

This is very initial commit to initiate discussion about Spark and OpenStack Swift integration.
At this point I provided information how to setup standalone Spark cluster and connect it to Swift using Hadoop 2.3.0. Current patch can be used by all to experiment integration between Swift and Spark. 

I am working to extend this patch and future patches will contain information how to configure Spark with previous Hadoop versions and how to configure Swift for other cluster deployment of Spark.

Will glad to hear all remarks / suggestion / comments from the community.
While it might make sense for this to eventually get into Spark, we need to look more carefully at the dependency that this brings. Since Spark runs different from Hadoop (Spark is really just a user level library), users can always include openstack support in their project dependencies (with the documentation you provide). For the time being, let's first update the documentation so it is obvious & clear & easy for users to add openstack support, and then we can discuss more about whether/when we should push the openstack dependency in Spark.