Set a session value with a timeout value with a redis session handler

[piraz]

Setting a session key/value withe the timeout parameter in the kwargs will be processed by the redis session handler by setting the key/value in the database and setting the ttl as the provided timeout parameter.

We need #408 implemented to provide this feature.

[piraz]

This task is more complex than just setting a ttl in a set command, the session is stored is encoded and added to a value in the redis database.

I think we can do that for all session handlers(even for file) using a callback.