1. Enhanced the full page invoice by allowing the "Avail Credit" value to hide if there is no balance. Also renamed to "Store Credit Bal".
  2. Fixed test print button for full page invoice. This is not supported so an extra check was added to inform the user properly.
  3. Fixed the followup (change due) screen to properly enable the open drawer button when applicable.
  4. Finalized cash drawer separation from the receipt printer options. These devices are now totally independent.