Index some fields to improve the speed of card exports.

ALTER TABLE `user_services` ADD INDEX `master_service_id_index` ( `master_service_id` )
ALTER TABLE `user_services` ADD INDEX `billing_id_index` ( `billing_id` )
ALTER TABLE `billing` ADD INDEX `billing_type_index` ( `billing_type` )
ALTER TABLE `tax_exempt` ADD INDEX `account_number_index` ( `account_number` )
ALTER TABLE `billing_details` ADD INDEX `billing_id_index` ( `billing_id` )
ALTER TABLE `payment_history` ADD INDEX `billing_id_index` ( `billing_id` )