message: Update AzureActionHandler docs in readme
diff: # VSCode Azure SDK for Node.js - UI Tools (Preview)
  This package provides common Azure UI elements for VS Code extensions:
  -* [AzureActionHandler](#azure-action-handler): Displays error messages and optionally adds telemetry to commands/events.
  +* [Telemetry and Error Handling](#telemetry-and-error-handling): Displays error messages and adds telemetry to commands/events.
  * [AzureTreeDataProvider](#azure-tree-data-provider): Displays an Azure Explorer with Azure Subscriptions and child nodes of your implementation.
  * [AzureBaseEditor](#azure-base-editor): Displays a text editor with upload support to Azure.
  -> NOTE: This package throws a `UserCancelledError` if the user cancels an operation. If you do not use the AzureActionHandler, you must handle this exception in your extension.
  +> NOTE: This package throws a `UserCancelledError` if the user cancels an operation. If you do not use `registerCommand`, you must handle this exception in your extension.
  -## Azure Action Handler
  +## Telemetry and Error Handling
  -Use the Azure Action Handler to consistently display error messages and track commands with telemetry. You should construct the handler and register commands/events in your extension's `activate()` method. The simplest example is to register a command (in this case, refreshing a node):
  +Use `registerCommand`, `registerEvent`, or ` callWithTelemetryAndErrorHandling` to consistently display error messages and track commands with telemetry. You must call `registerUIExtensionVariables` first in your extension's `activate()` method. The simplest example is to register a command (in this case, refreshing a node):
  ```typescript
  -const actionHandler: AzureActionHandler = new AzureActionHandler(context, outputChannel, reporter);
  -actionHandler.registerCommand('yourExtension.Refresh', (node: IAzureNode) => { node.refresh(); });
  +registerUIExtensionVariables(...);
  +registerCommand('yourExtension.Refresh', (node: AzureTreeItem) => { node.refresh(); });
  ```
  Here are a few of the benefits this provides:
  * Parses Azure errors of the form `{ "Code": "Conflict", "Message": "This is the actual message" }` and only displays the 'Message' property
  * Displays single line errors normally and multi-line errors in the output window
  -* If you pass a TelemetryReporter, tracks multiple properties in addition to the [common extension properties](https://github.com/Microsoft/vscode-extension-telemetry#common-properties):
  +* Tracks multiple properties in addition to the [common extension properties](https://github.com/Microsoft/vscode-extension-telemetry#common-properties):
  * result (Succeeded, Failed, or Canceled)
  * duration
  * error
  If you want to add custom telemetry proprties, use the action's context and add your own properties or measurements:
  ```typescript
  -actionHandler.registerCommand('yourExtension.Refresh', function (this: IActionContext): void {
  +registerCommand('yourExtension.Refresh', function (this: IActionContext): void {
  this.properties.customProp = "example prop";
  this.measurements.customMeas = 49;
  });
  @@ -32,7 +32,7 @@ actionHandler.registerCommand('yourExtension.Refresh', function (this: IActionCo
  Finally, you can also register events. By default, every event is tracked in telemetry. It is *highly recommended* to leverage the IActionContext.suppressTelemetry parameter to filter only the events that apply to your extension. For example, if your extension only handles `json` files in the `onDidSaveTextDocument`, it might look like this:
  ```typescript
  -actionHandler.registerEvent('yourExtension.onDidSaveTextDocument', vscode.workspace.onDidSaveTextDocument, async function (this: IActionContext, doc: vscode.TextDocument): Promise<void> {
  +registerEvent('yourExtension.onDidSaveTextDocument', vscode.workspace.onDidSaveTextDocument, async function (this: IActionContext, doc: vscode.TextDocument): Promise<void> {
  this.suppressTelemetry = true;
  if (doc.fileExtension === 'json') {
  this.suppressTelemetry = false;
  