v0.5.6

Fixed

• A queued item keeps the arguments it was submitted with. QueuedItem::plan
  put the whole submitted body into args, so a client reading the queue back
  found the plan's metadata nested one level down and rendered the columns it
  fills -- sample, edge energy, point count -- as blank. args and kwargs
  are now separate fields and plan_args() recombines them for PlanFactory.
• The running item is reported as the item that was queued. current_item
  replaces current_plan_name in the server state, so queue_get hands back
  the running item beside the pending ones instead of a name; a name is not an
  item, and a client rendering the queue as one table had every column but the
  plan empty on the one row that was actually running.