AuxCounters & benchmark modes

[Dmitry Chuyko]

Hello.

Current AuxCounters's javadoc says: "NOTE: This functionality is not 
available for all {@link BenchmarkMode}-s". It works in throughput mode 
but not for singleshot (-bm ss) mode. Maybe it makes sense to allow all 
modes. For example consider a state that collects some system statistics 
after each invocation.

One more thing here is a name of units in output which for custom 
counters is the same as for main microbenchmark result (e.g. ops/ms). It 
would be nice to print nothing at least or to have some way to specify 
units, something like @Units("bytes").

Dmitry