Add support for distributed session manager implementations

[marceloverdijk]

• Redis?
• Memcache?
• JDBC?

[marceloverdijk]

Just a few to mention that might be interesting to implement:

• Redis
• Memcached
• Ehcache
• Hazelcast
• JCS
• AppEngine
• Plain JDBC
• MongoDB
• Guava Cache (in-process cache; not distributed)