Multi-cloud support of data management solution

[mebster]

From the description of the external object (http://ssdocs.sixsq.com/en/latest/tutorials/ss/data-management-model.html), we also need examples of how to achieve some of the high-level goals the feature claims:

• An abstraction that allows uniform access across multiple clouds
• Rich search capabilities to find appropriate data objects
• Direct access to data within objects to maximize performance
• The ability to cache and to replicate data objects effectively

especially the cross cloud or multi-cloud aspect, including replication.