{WIP} Rework agent-collect and agent-mono

Reduce memory consumption : use a cache for counters values, so even with the growing number of revisions, the memory should stay the same.
Generate JSON files instead of sag files : used by the web interface, allow generation of more interactive graphs
{WIP} Refactor compare tool

 - Do not show benchmarks with missing data
 - Do not read benchmarks and configs file if "--no-run" is passed
 - Label now vertical, to avoid overlapping