title: VS2017 + ReactJS + use of entity framework throws and error on migration
body: <p>I've started a new React+Redux project in VS2017 (.net core 2.0). Default template comes without database use, so I just added use of entity framework manually. It compiles well but when I try to add a migration using command</p>
  
  <pre><code>dotnet ef migrations add "Initial"
  </code></pre>
  
  <p>I'm getting the next error:</p>
  
  <pre><code>An error occurred while calling method 'BuildWebHost' on class 'Program'. Continuing without the application service provider. Error: One or more errors occurred. (Webpack dev middleware failed because of an error while loading 'aspnet-webpack'. Error was: Error: Cannot find module 'aspnet-webpack'
  at Function.Module._resolveFilename (module.js:469:15)
  at Function.Module._load (module.js:417:25)
  at Module.require (module.js:497:17)
  at require (internal/module.js:20:19)
  at Object.&lt;anonymous&gt; (C:\Users\sibvic\AppData\Local\Temp\iu25u5dg.r0n:83:19)
  at __webpack_require__ (C:\Users\sibvic\AppData\Local\Temp\iu25u5dg.r0n:20:30)
  at createWebpackDevServer (C:\Users\sibvic\AppData\Local\Temp\iu25u5dg.r0n:62:26)
  at C:\Users\sibvic\AppData\Local\Temp\ftqvg4wq.l1l:114:19
  at IncomingMessage.&lt;anonymous&gt; (C:\Users\sibvic\AppData\Local\Temp\ftqvg4wq.l1l:133:38)
  at emitNone (events.js:86:13)
  Current directory is: C:\projects\test\bin\Debug\netcoreapp2.0
  )
  Unable to create an object of type 'ApplicationDbContext'. Add an implementation of 'IDesignTimeDbContextFactory&lt;ApplicationDbContext&gt;' to the project, or see https://go.microsoft.com/fwlink/?linkid=851728 for additional patterns supported at design time.
  </code></pre>
  
  <p>It looks like this features is too new. Not much information I can find. And can't figure out what's wrong by myself (at least yet, rubber duck method doesn't work either).</p>
  
  <p>Any idea how to fix it?</p>