Intuit has revealed QuickBooks for Mac 2013, the next major update of the company’s small business accounting software. Relatively few changes to the app have been detailed, but Intuit does say 2013 will simplify a number of common tasks, such as invoicing, reconciling accounts, and adding contacts. A new online payment service will be offered through Intuit, and users will be able to attach documents to items such as contracts, proposals, and receipts….