JDG/Infinispan cache store backend implementation

[ruivieira]

Ability to use a JDG/Infinispan cache store by providing:

• CACHE_TYPE, a string of 'infinispan' or 'jdg'
• CACHE_HOST, the JDG server address (e.g. '127.0.0.1')
• CACHE_PORT, the JDG server port (e.g. 8888)
• CACHE_NAME, the cache db name (e.g. 'namedCache')

Upon loading a new model, a new Cache abstract method, invalidate, is called which empties the JDG cache store.

TODO: At the moment JDG REST security must be disabled.

[ruivieira]

@elmiko thanks for the comments! ptal at the error handling.

[elmiko]

lgtm, thanks @ruivieira !