statistics: merge() method added.
introduce end-of-line normalization.
rapidjson: replace \r\n with \r.
rapidjson: allow not object and not array values to be written as root.
statistics: make timestamp stat mandatory.
statistics: when extracting quantiles from histogram stop on the last bin.

Still extracting 100%-quantile could lead to fail due to double rounding errors.
chrono: TICK time unit renamed to CYCLE.
chrono: TSC clock type renamed to INTERNAL.
chrono: tsc_clock renamed to internal_clock.
chrono: duration and time_point implementation moved out from header file.