Improve the workflomics visualisation of the metrics

[vedran-kasalica]

the current visualization presents the metrics as 2 independent values:

Proposed improvements:

• Group the 2 values together
• Rename Pubmetric to a more descriptive metric name (e.g., co-citations)

[magnuspalmblad]

The OS compatibility should also be grouped together I think. Maybe just with a thin horizontal line between categories?

[vedran-kasalica]

@magnuspalmblad I agree. I added the issue under Workflomics front-end (see Workflomics/workflomics-frontend#80) as it was not pubmetric-specific.