Allow setting log level through environment variables

[ttzn]

Fixes #4580

For some reason PropertiesLoggingLevelsConfigurer was only loading raw keys.

[jameskleeh]

This could have implications if the intent is to configure the log level of a non conventional package name. For example if someone had com.myApp as a package name, the resulting value would now be com.my-app.

[graemerocher]

@jameskleeh Java package names should be lower case so I think that is non-issue

[ttzn]

@jameskleeh good catch, this MR introduces a regression for those kinds of package names. Maybe we can load both raw keys for compatibility and generated keys to allow environment variables, with a little warning in the doc.

[graemerocher]

Thanks for the contribution!