Add system keyboard interface and add sleep, power and wake keys.

right/src/usb_composite_device.h

@@ -20,6 +20,7 @@
         class_handle_t basicKeyboardHandle;
         class_handle_t genericHidHandle;
         class_handle_t mediaKeyboardHandle;
+        class_handle_t systemKeyboardHandle;
         uint8_t attach;
         uint8_t currentConfiguration;
         uint8_t currentInterfaceAlternateSetting[USB_DEVICE_CONFIG_HID];