The amount of latency a service needs before being considered "slow" is
configurable in config.json. By default, it is 2000ms (2s).
A side effect of this change is that the "service unresponsive" icon
that is shown when a service is unreachable has been changed to an X
instead of a !.
The slow icon now uses the ! icon.
Additionally, icon "titles" were added to aid any screen readers.
