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).
That's correct. This way saves an additional if over starting with a null string, iterating through the fields and then checking the result (and setting CreatedDate if required). The iteration can't be avoided unfortunately, but the break should hopefully help mitigate any CPU time usage impact.