Use class names with package name when getting logger, instead of just using only the class name.

Instead of just using the name of the class, the full canonical class name is used. This allows filtering on the log level directly in the configuration of the used logging framework for all classes in ReactiveMongo, instead of having to do that for each class separately.
Merge pull request #20 from MarkvanderTol/loggernames

Use class names with package name when getting logger, instead of just using only the class name.