Update fflib_SObjectSelector.cls getOrderBy() default behaviour

Changed the default value of getOrderBy() as not all objects have a 'Name' field (e.g. OpportunityContactRole, CampaignMember).
Are you happy the existing unit test for this class does not need any further work? By the looks of it the existing tests will cover this new code, so i don't think there is any regression there. And the unit testing in the fflib_SObjectDescribeTest ought to suffice. So just checking if you feel there is any further scope for adding a test method or two to the fflib_SObjectSelectorTest class or not? Thoughts?