logging level at WARNING by default

[ThibaultDECO]

setting the logging level at WARNING by default, which is more user-friendly

Summary

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• Code: BSD 3-clause (https://opensource.org/licenses/BSD-3-Clause)

[ThibaultDECO]

@WardBrian ok, I left the pre-existing handlers at DEBUG level

[WardBrian]

Thanks!

I'm in favor of this change in general, but I want to take some time to go through our existing logging calls and make sure there are no infos that should be warnings (or vice-versa)