Session driver - autoload session config & redis fixes

1) Config. Instead of passing config items from autoloader to library constructor - it is better to load config in library constructor, as the library can be loaded manually without any params. Now all the Session params (even specific driver params) can be set in config files. i.e. `$config['sess_driver'] = 'redis'; $config['sess_save_path'] = '/var/run/redis-cache.sock';`

2) Redis. Better unix domain support with params in connection string, Support for permanent sessions (`$config['sess_expiration']		= 0`) now does not sets the expiration at all, instead of removing it instantly after creating.