Test that factories can be added manually
Check if the factory required name is used
Improve tests

 - Do not mock ServiceLoader entirely, just an injectable.
 - Inject the custom ServiceLoader in the RavenFactory class directly
 - Create a new Iterator every time the Iterator() method is called
 - Unregister manually registered factories
 - Do not register the factories in the expectations
Add a toString method to RavenFactory
Add a test to check that Raven creation failures are caught
Add a line to ensure that the consoleHandler will print everything that is logged