title: Property 'payload' does not exist on type 'Action' when upgrading @ngrx/Store
body: <p>I have the <code>@ngrx/store</code> package in my angular (4.x) app, and am upgrading from v<strong>2.2.2</strong> -> v<strong>4.0.0</strong>. I can see that the migration notes say:</p>
  
  <blockquote>
    <p>The payload property has been removed from the Action interface.</p>
  </blockquote>
  
  <p>However, the example they give seems completely counter intuitive (in my view...). </p>
  
  <p>I have a reducer function which looks like this:</p>
  
  <pre><code>export function titleReducer(state = { company: 'MyCo', site: 'London' }, action: Action): ITitle {
      switch (action.type) {
          case 'SET_TITLE':
              return {
                  company: action.payload.company,
                  site: action.payload.site,
                  department: action.payload.department,
                  line: action.payload.line
              }
          case 'RESET':
              return {
                  company: 'MyCo',
                  site: 'London'
              }
          default:
              return state
      }
  }
  </code></pre>
  
  <p>Which as expected now throws typescript error:</p>
  
  <blockquote>
    <p>[ts] Property 'payload' does not exist on type 'Action'</p>
  </blockquote>
  
  <p>But I have no idea from the migration guide what this should be changed too. Any ideas?</p>