Allow displaying more tasks in task info

[Kobzol]

I think that it should be possible to select multiple tasks, e.g. hq task info 1 2-3. The task tables should just be printed below one another.

Also it would be nice if JOB-ID could be specified using the last placeholder. I don't think that we should enable querying across multiple jobs, since the task IDs might not be the same for them.