Pyaf 5.0 Final Touch 6 : Disable Timing Loggers by default

[antoinecarme]

Timing operations are producing a lot of noise/blabla in jupyter notebooks. Hierarchical models are building a lot of forecasting models and their logs are difficult to read now.

Do this:

1. Disable time logging by default. cTimer logging level = logging.INFO
2. Add a way to enable logging + tests with time logger activated. cTimer logging level = logging.DEBUG
3. Perform a real logging of time spent in most important operations (train + forecast + ...) independently of time loggers. The training time is an important performance indicator and must be logged the same way the model MAPE is logged.
4. Regenerate jupyter notebooks.
5. Double check the CI results.

[antoinecarme]

FIXED.