ISPN-3318 Embedded rolling upgrade using CLI enabling cache store data migration.

* Providing rolling upgrade capabilities for embedded caches is the key step for providing on-the-fly cache store data migration.
* Data stored in old formats in embedded Infinispan 5.2.x instances can easily be migrated to Infinispan 6.x embedded instances plugged with different cache stores, or cache stores with updated storage format.

For testing rolling upgrades, a created a [small app](https://github.com/galderz/rolling) that shows rolling upgrades in action. I hope to enhance it further to show a rolling upgrade of an application using Infinispan 5.2.x, configured with a file cache store, to Infinispan 6.x with single file cache store, which is the core of what ISPN-3318 is trying to show off.

The code is not complete, there's a few things missing:
- CLI cache loader XML parser, schema, unit tests (!!) and rest of bells and whistles.
- Testing (and support if any changes required?) for custom types in the cache.

Putting this out there so that it can be reviewed in parallel before heading out for vacation on Friday.