removing Web UI tutorials, updating remaining 4 to current release, + review pass

src/site/docs/tutorials/indexeddb/examples/count_down/out/web/xcountdown.dart

-// Some things we need.
-import 'package:polymer/polymer.dart';
-import 'dart:html';
-import 'dart:async';
-import 'count_down.dart';
-
-@CustomTag('x-count-down')
-class CountDownComponent extends PolymerElement {
-  
-  // Observe errorMsg.
-  // It displays a message for the user.
-  @observable String get errorMsg => __$errorMsg; String __$errorMsg = ''; set errorMsg(String value) { __$errorMsg = notifyPropertyChange(#errorMsg, __$errorMsg, value); }
-
-  // These are bound to input elements.
-  @observable String get newMilestoneName => __$newMilestoneName; String __$newMilestoneName = "New Year's Day"; set newMilestoneName(String value) { __$newMilestoneName = notifyPropertyChange(#newMilestoneName, __$newMilestoneName, value); }
-  @observable String get newMilestoneDate => __$newMilestoneDate; String __$newMilestoneDate = '2014-01-01'; set newMilestoneDate(String value) { __$newMilestoneDate = notifyPropertyChange(#newMilestoneDate, __$newMilestoneDate, value); }
-  @observable String get newMilestoneTime => __$newMilestoneTime; String __$newMilestoneTime = '00:00:00'; set newMilestoneTime(String value) { __$newMilestoneTime = notifyPropertyChange(#newMilestoneTime, __$newMilestoneTime, value); }
-  
-  @observable MilestoneApp get appObj => __$appObj; MilestoneApp __$appObj = appObject; set appObj(MilestoneApp value) { __$appObj = notifyPropertyChange(#appObj, __$appObj, value); }
-  
-  /*
-   * Click handlers.
-   * NOTE: Minus - button handler is in xmilestone web component.
-   */
-  // Plus + button click handler.
-  void addMilestone(Event e, var detail, Node target) {
-    String str = newMilestoneDate + ' ' + newMilestoneTime;  
-    DateTime occursOn = DateTime.parse(str);
-
-    appObject.addMilestone(newMilestoneName, occursOn);
-  }
-
-  // Clear button click handler.
-  void clear(Event e, var detail, Node target) {
-    errorMsg = '';
-    appObject.clear();
-  }
-   
-  /*
-   * Life-cycle bizness
-   */
-  void inserted() {
-    appObject.start()
-      .catchError((e) {
-        ($['addbutton'] as ButtonElement).disabled = true;
-        ($['clearbutton'] as ButtonElement).disabled = true;
-
-        errorMsg = e.toString();
-      });
-  }
-  
-  void removed() {
-    appObject.stop();
-  }
-} // end class