swipe: Touchscreen workspace swipe (#4489)

* Workspace Swipe: Refactor update and end functions

* Touch: Implement workspace swipe better

ignoring additional fingers and new touches

allow gaps-right and gaps-left to be different

src/managers/input/InputManager.hpp

@@ -231,6 +231,8 @@ class CInputManager {
 
     // swipe
     void beginWorkspaceSwipe();
+    void updateWorkspaceSwipe(double);
+    void endWorkspaceSwipe();
 
     void setBorderCursorIcon(eBorderIconDirection);
     void setCursorIconOnBorder(CWindow* w);