v2.4.0: Feature release

BACKWARD INCOMPATIBLE CHANGE IN JSON: depending on how you use the cmonitor JSONs, this release may require an update in your scripts / post-processing code

• Review JSON format for tracked processes by grouping together similar KPIs: introduce new JSON objects containing all related "cpu", "memory", "io", "proc_info" fields previously prefixed with "cpu_", "memory_", "io_", etc