[BENCH] Statistics refactoring

[edanor]

In file microbenchmarks/utilities/TimingStatistics.h, a class TimingStatistics is defined, together with a more general Statistics template.

The task is to remove completely TimingStatistics and replace its use with templated version. In addition to that, all files should also calculate some numeric error measure, so that the it would be possible to compare precision of different implementations (see RMS error in matmul benchmark).