Update ctkLogger

[jcfr]

• Update ctkLogger adding support for log level: Set default level based on the build config.
• Update ctkErrorLogLevel enum values defining "Unknown" as 0

[jcfr]

@Punzo @lassoan There changes were originally part of https://github.com/commontk/CTK/pull/1165 and have been factored out into an independent pull request.

[jcfr]

Now that we removed support for Qt4, for new classes, I think we should instead standardize on using QLoggingCategory and avoid ctkLogger.

See https://doc.qt.io/qt-5/qloggingcategory.html

[Punzo]

@Punzo @lassoan There changes were originally part of #1165 and have been factored out into an independent pull request.

ok, perfect!

[jcfr]

I revisited the default level associated with the ctkLogger functions and also added a multiple tests.