Merge gesture structs/enums

- Now only 1 GestureDirection enum
- Now only 1 registerGesture() call
- The 4 kinds of gesture (Pinch/Swipe) and (Touchpad/Touchscreen) in globalshortcuts.h/cpp are merged into 1 GestureShortcut
- Change from range to set of finger counts in gestures

No behavior should change, just a refactor.