Shipped with a wall charger and USB cable, PaySaber Clip ($349) is USAePay's first portable point-of-sale system for all iOS users, bringing features from its prior iPhone- and iPod touch-compatible units to a design that works equally well with the iPad. Contrasting with the diminutive Square Reader and Intuit GoPayment systems, PaySaber Clip has an eight-hour rechargeable battery inside to power a three-track bi-directional credit card reader and…