Add logging support

[ndem0]

Is your feature request related to a problem? Please describe.
At the moment, the only output of a typical PINA application is the loss trend during the training. Better outputs (maybe modulable in verbosity) would be a nice feature, especially for debugging purposes.

Describe the solution you'd like
https://docs.python.org/3/library/logging.html#module-logging library can be used in order to let the user set the wanted verbosity.

Describe alternatives you've considered
loguru but it's a further dependency.

[dario-coscia]

Opened in #126 a new issue for the next version release. We will not insert loggers in the current release.