Redis output: Write using SET and TTL

[ghost]

Currently the Redis output can only write to queues (lists) using LPUSH.

Having the possibility to use SET in conjunction with setting a TTL would enable IntelMQ to generate blacklists and alike

For that purpose, add a new optional parameter for setting the TTL. If the queue_name is not given, the SET-mode is activated. However, SET-mode is only useful for the single_key-mode, so that's required.