Reporting: Make the AppNexus report interval and DynamicAllocation delivery data look-back configurable
 * Add AppNexus.ReportInterval worker role setting and corresponding AppNexusReportIntervalType enum
 * Modify AppNexusApiClient to retrieve AppNexus.ReportInterval from config and use mapped JSON value in report requests
 * Add DynamicAllocation.DeliveryHistoryLookBack timespan value to worker role settings
 * Modify GetCampaignDeliveryDataActivity.HistoryLookBack to get its value from the role setting