Implement a log rotation every N benchmarks

[SuperFola]

We should cut the data files in N elements so that the website do not load a million results and try to render it all at once.

Files could be stored as (i*N)-original-name, so that we can find them easily.

We should also limit the number of elements in the current file to N max. All the excess should go to another file (N*i)-original-name.

The old files will then file up slowly and we will still have enough data in the current files for the graphs.