Storage and transmission usage not shown technology-specific on the report

[sonercandas]

In the current state of the reporting function, the storage levels and (dis-)charge are aggregated for each site rather than being shown specifically for each storage technology in the sites. Same for import/export along transmission lines.

Especially for case studies comparing various transmission or storage technologies, it could be helpful to modify the report such that it displays the usage of each technology separately (as for processes) on the report file.