netmap dead link visualisation / aggregated link problem visualisation

[Peter Gervai]

Netmap (geomap) should show distinctively when a link is down. [since you use 'red' for link load it probably should use blue or black]

Netmap should draw separate lines for separate (known) links, and color them accordingly (this should help to see asymmetrical problems). When one of the multiple links are down it should show that way.

If we talk about visualisations it may be useful to change linetype when the line observes discards or input errors, but it's not easy to specify the thresholds (they probably ought to be configurable link-by-link anyway).