Add RedisSharedClient that can share one connected driver for more clients

[forrest79]

Proof of concept yet...

• new RedisSharedClient based on RedisClient, but share one driver for many connections
• I am not sure with names (obviously), I made ConnectionPool, but it is pool of drivers... For me connection better describes what it is, but it could be confusing because it is drivers...
• I don't make DI config yet, I have no idea, what config can be set to use RedisSharedClient instead of RedisClient
• disadvantage: if user get driver with getDriver() method, than user have to expected, that some RedisSharedClient can change database...

[fprochazka]

Here should be your name ;)

[forrest79]

He, yes, thanks :-)

[forrest79]

When you will have a minute, can you take a look at last notes? :-) Thanks

[fprochazka]

I like it :) I just need to look at the code more thoroughly and then we can merge it.