Reduce Logging noise

[Nawv]

Simplifies how loggers are used/set, and reduces noisy informational logging:

• Use a static variable to store the logger instance, so it can easily be changed globally.
• Move the logger instance to a new Zamzar class.
• Deprecate old ZamzarClient get/set logger methods - interact directly with the Zamzar class instead.
• Add a debug config option that defaults to false, and lock informational logging behind it.
• Reduce the 'noise' created by unhelpful logging.
• Add new tests for the logging system.