Specs: define how importing element registrations works, move built-in elements to a separate modul…

sky/specs/gestures.md

 Gestures
 ========
 
 ```dart
-SKY MODULE
-<!-- part of dart:sky -->
-
-<script>
 abstract class GestureEvent extends Event {
   Gesture _gesture;
   Gesture get gesture => _gesture;
 }
 
 class GestureState {
   bool cancel = true; // if true, then cancel the gesture at this point
   bool capture = false; // (for PointerDownEvent) if true, then this pointer is relevant
   bool choose = false; // if true, the gesture thinks that other gestures should give up
   bool finished = true; // if true, we're ready for the next gesture to start
@@ skipping 227 matching lines @@
       var pointerState = _pointers[pointer];
       if ((!pointerState.chosen) && (pointerState.gestures.length == 1)) {
         pointerState.chosen = true;
         pointerState.gestures[0].choose();
       }
     }
   }
 
 }
 /*
-</script>
 ```
 
 Gestures defined in the framework
 ---------------------------------
 
 ```dart
 SKY MODULE
 <!-- not in dart:sky -->
 <!-- note: this hasn't been dartified yet -->
 
@@ skipping 182 matching lines @@
   FlingRightGesture = FlingGesture;
 }
 class FlingUpGesture extends FlingGesture {
   FlingUpGesture = FlingGesture;
 }
 class FlingDownGesture extends FlingGesture {
   FlingDownGesture = FlingGesture;
 }
 </script>
 ```