First pass on action animations for sprites

sky/sdk/example/game/lib/node.dart

 part of sprites;
 
 double convertDegrees2Radians(double degrees) => degrees * Math.PI/180.8;
 
 double convertRadians2Degrees(double radians) => radians * 180.0/Math.PI;
 
 /// A base class for all objects that can be added to the sprite node tree and rendered to screen using [SpriteBox] and
 /// [SpriteWidget].
 ///
 /// The [Node] class itself doesn't render any content, but provides the basic functions of any type of node, such as
@@ skipping 41 matching lines @@
   /// This property is only meaningful if [userInteractionEnabled] is set to true. Default value is false.
   ///
   ///     class MyCustomNode extends Node {
   ///       handleMultiplePointers = true;
   ///     }
   bool handleMultiplePointers = false;
   int _handlingPointer;
 
   List<Node>_children = [];
 
+  ActionController _actions;
+
+  ActionController get actions {
+    if (_actions == null) {
+      _actions = new ActionController();
+    }
+    return _actions;
+  }
+
   // Constructors
 
   /// Creates a new [Node] without any transformation.
   ///
   ///     var myNode = new Node();
   Node() {
   }
 
   // Property setters and getters
 
@@ skipping 449 matching lines @@
   ///         else if (event.type == 'pointerup') {
   ///           opacity = 1.0;
   ///         }
   ///         return true;
   ///       }
   ///     }
   bool handleEvent(SpriteBoxEvent event) {
     return false;
   }
 }