Introduce a third panel for tours

[alexsegura]

See #3552

This would solve most of the problems of tour edition (reordering, drag'n'dropping a new task), also in terms of implementation with react-beautiful-dnd draggable/droppable structure.

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In order to solve the problem of Tour edition we are ading a third panel to the dashboard. This will be the Unassigned Tours Panel and will allow the Dispatcher to:

• Reorder Tasks within a Tour using drag-n-drop
• Add new Tasks to a Tour using drag-n-drop
• Create empty Tours
• Rename Tours
• Delete Tours

A Tour can be assigned to a Rider using drag-n-drop.

Some screenshots:

Image: vertical panels, all tours collapsed

Image: vertical panels, tour expanded

Image: horizontal panels, some tours expanded

Image: horizontal panels, some tours expanded, assigned tour

[Paul-Eraman-CoopCycle]

@alexsegura This is completely true. However, to implement such a broad feature, there needs to be significantly more information here. Please elaborate about what this third dashboard panel would involve and how it many be represented.

[jimakker]

This already has a PR but I'm using that branch for #3597. I will discard the PR and we'll merge the other one.