Allow reordering tasks of a tour before assigning it

[alexsegura]

See #3552
Needs #3595

Once the "tours" panel has been introduced, the dispatcher should be able to reorder tasks of a tour inside this panel.
To implement this, we will need to allow PUT operations on tours on the API.

• Add a PUT operation in the itemOperations section of the Tour entity. It should look like the definition of the POST operation. We will probably need to make a small change in TourInputDataTransformer, to make the name property optional.
• Add a functional test for the PUT operation in the dispatch.feature file. The payload of the PUT operation should look like this:

{
  "tasks": [
     "/api/tasks/1",
     "/api/tasks/2",
     "/api/tasks/3"
  ]
}

• As all panels share the same DragDropContext, everything needs to be implemented in the same handleDragEnd function.