Add a printer factory to simplify construction of printer drivers (#11)

Co-authored-by: Moritz Martinius <mm@cloudprinters.de>
Reviewed-on: moritz/ptouch-prnt#11

src/libusbwrap/UsbDevice.cpp

@@ -104,12 +104,8 @@ bool UsbDevice::bulkTransfer(uint8_t endpoint, std::vector<uint8_t>& data, int*
     return true;
 }
 
-const uint16_t UsbDevice::getVid() {
-    return mLibusbDevDesc.idVendor;
-}
-
-const uint16_t UsbDevice::getPid() {
-    return mLibusbDevDesc.idProduct;
+const usbId UsbDevice::getUsbId() {
+    return {mLibusbDevDesc.idVendor, mLibusbDevDesc.idProduct};
 }
 
 const device::Speed UsbDevice::getSpeed() {