Implementation for Redis Cache Storage

 Greetings!

I have implemented a cache handler for Redis storage. It uses PHP Redis extension or Predis PEAR package if any of these are available. It also adds 2 global configuration options for Redis Host IP/Socket and Redis Port.

Only had a chance to test on Windows.

References:
Predis: https://github.com/nrk/predis
PHP Redis Extension: https://github.com/nicolasff/phpredis

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