Remove Yeoman generator - replace it with deprecation notice.

Author: SteveSandersonMS

templates/package-builder/src/yeoman/.gitignore

@@ -1,14 +1,15 @@
-Generates ASP.NET Core projects for single-page applications.
+# Please use "dotnet new" templates instead
 
-Can generate projects with:
+As of .NET Core 2.0, it's no longer necessary to use Yeoman to create new Single-Page Application projects.
 
- * Angular
- * Aurelia
- * Knockout
- * React
- * React with Redux
- * Vue
+Using the .NET Core 2.0 SDK, you can run any of the following commands in an empty directory, without needing to install any external packages first:
 
-For more information about features and usage, see [this blog post](https://blogs.msdn.microsoft.com/webdev/2017/02/14/building-single-page-applications-on-asp-net-core-with-javascriptservices/).
+ * `dotnet new angular`
+ * `dotnet new react`
+ * `dotnet new redux`
 
-To learn more about the underlying technologies, or to report any issues, see [this project's GitHub repo](https://github.com/aspnet/JavaScriptServices).
+Or, if you want to create an Aurelia, Knockout, or Vue application, you should run `dotnet new --install Microsoft.AspNetCore.SpaTemplates::*` first. This will add `aurelia`, `knockout`, and `vue` templates to `dotnet new`.
+
+#### This Yeoman generator is DEPRECATED
+
+Please don't use `generator-aspnetcore-spa` to create new projects. Its output is outdated and no longer maintained. Instead, use `dotnet new` as described above (or if you're on Windows and use Visual Studio, you can just use *File->New Project* to create Angular, React, or React+Redux projects).

templates/package-builder/src/yeoman/README.md

@@ -1,12 +1,9 @@
 {
   "name": "generator-aspnetcore-spa",
   "version": "1.0.0",
-  "description": "Single-Page App templates for ASP.NET Core",
+  "description": "DEPRECATED. Do not use. Use 'dotnet new' to create ASP.NET Core Single-Page Application projects instead.",
   "author": "Microsoft",
   "license": "Apache-2.0",
-  "files": [
-    "app"
-  ],
   "keywords": [
     "yeoman-generator"
   ],
@@ -18,12 +15,5 @@
     "url": "https://github.com/aspnet/JavaScriptServices.git"
   },
   "dependencies": {
-    "chalk": "^1.1.3",
-    "glob": "^7.0.3",
-    "node-uuid": "^1.4.7",
-    "to-pascal-case": "^1.0.0",
-    "yeoman-generator": "^0.20.2",
-    "yeoman-option-or-prompt": "^1.0.2",
-    "yosay": "^1.1.1"
   }
 }