joomla-framework: Implemented Redis Cache Handler

Greetings!

I have implemented a cache handler for Redis storage. It uses PHP Redis extension.

It accepts 2 Registry configuration options for Redis Host IP/Socket and Redis Port as follows:
redis.host // default: 127.0.0.1
redis.port // default: 6379

Both can be skipped or unix socket path can be provided instead of host.

Only had a chance to test on Windows. But I'm pretty sure it should be fine on *nix based oses.

References:
Predis: https://github.com/nrk/predis
Joomla CMS PR: https://github.com/joomla/joomla-cms/pull/2078