RTT matrix dynamic limits

[emileaben]

for the RTT matrix allow for customisation of the thresholds

for instance:

• start with defaults that worst 5% is always red, next 10% yellow, then green for rest
• allow users to change these limits (with sliders-ui-component for example, see DNSMON)
  • bonus points for having this next to a graph that shows the distribution of RTTs (histogram)