Add a method to retrieve last run results

[Neyri]

It would be nice to be able to retrieve the consumption of the last training.
Maybe we could add a method to get this. I'm thinking of something like :

power_meter = PowerMeter(*args)
with power_meter(*args, **kwargs):
    # do_something

# This would be nice
co2_emission, energy_consumption = power_meter.get_last_log(columns=["Carbon emissions", "Energy consumption"])

Naming and arguments are open to discuss