Update the benchmark structure to the new SpineToolbox version 0.8.0

[datejada]

Update the case study in the benchmark to have the new structure with entities from SpineToolbox 0.8.0.

Add the following parameters and relationships to make a more complex case study to benchmark:

• [ ] unit_node_node
• [ ] fix_ratio_out_in_unit_flow
• [ ] connection_node_node
• [ ] fix_ratio_out_in_connection_flow
• [ ] min_up_time (down)
• [ ] meshed network
• [ ] add state to some nodes (storage)
• [ ] ramps
• [ ] reserves

@jkiviluo would you mind sending an example of the new structure? If possible, with an equivalent of the old one, to make the 1:1 match. Thanks!