Services to gather information on the performance of events by categories

Provides PerfMap to manage all the categories and PerfEntry for per-category statistics.

for i in 100.times do
    var clock = new Clock

    # Do some "work" here
    nanosleep(0, 1000000)

    # Register the perf
    sys.perfs["sleep 1ms"].add clock.lapse

    # Do some other "work" here
    nanosleep(0, 5000000)

    # Register the perf
    sys.perfs["sleep 5ms"].add clock.lapse
end

assert sys.perfs["sleep 1ms"].count == 100
assert sys.perfs["sleep 1ms"].avg.is_approx(0.001, 0.001)
assert sys.perfs["sleep 5ms"].avg.is_approx(0.005, 0.005)