[ASNodeController] Move ASNodeController to beta header (#2966)

* Move ASNodeController to beta header

* Make it public

* Change ASNodeController+Beta to .mm

AsyncDisplayKit/ASNodeController+Beta.m

@@ -0,0 +1,58 @@
+//
+//  ASNodeController.mm
+//  AsyncDisplayKit
+//
+//  Created by Hannah Troisi for Scott Goodson on 1/27/17.
+//  Copyright © 2017 Facebook. All rights reserved.
+//
+
+#import "ASNodeController+Beta.h"
+
+#import "ASDisplayNode+FrameworkPrivate.h"
+
+@implementation ASNodeController
+
+@synthesize node = _node;
+
+- (instancetype)init
+{
+  self = [super init];
+  if (self) {
+    
+  }
+  return self;
+}
+
+- (void)loadNode
+{
+  self.node = [[ASDisplayNode alloc] init];
+}
+
+- (ASDisplayNode *)node
+{
+  if (_node == nil) {
+    [self loadNode];
+  }
+  return _node;
+}
+
+-(void)setNode:(ASDisplayNode *)node
+{
+  _node = node;
+  _node.interfaceStateDelegate = self;
+}
+
+// subclass overrides
+- (void)didEnterVisibleState {}
+- (void)didExitVisibleState  {}
+
+- (void)didEnterDisplayState {}
+- (void)didExitDisplayState  {}
+
+- (void)didEnterPreloadState {}
+- (void)didExitPreloadState  {}
+
+- (void)interfaceStateDidChange:(ASInterfaceState)newState
+                      fromState:(ASInterfaceState)oldState {}
+
+@end