title: how to export stacknavigator with screenprops?
body: <p>I'm trying to export a stacknavigator such that child screens can have some screen properties.  I tried something like this:</p>
  
  <pre><code>//Router.js
  import React, { Component } from 'react';
  import {StackNavigator} from 'react-navigation';
  import { AppRegistry } from 'react-native';
  import Home from './Home';
  
  let Router = 
  {
    Home: {screen: Home, screenProps:"hello"},
  }
  
  const Navigator = StackNavigator(Router);
  export default Navigator;
  </code></pre>
  
  <p>Then I have </p>
  
  <pre><code>//Home.js
  
  import React, { Component } from 'react';
  
  /* define navOptions */
  
  export default class Home extends Component {
    static navigationOptions = navOptions;
  
    componentDidMount()
    {
      const db = new DB(this);
      db.open();
    };
      constructor(props)
      {
          super(props);
      }
  render ()
  {
  console.log(this.props);
  }
  }
  </code></pre>
  
  <p>But <code>this.props.screenProps</code> is empty.</p>
  
  <p>I then tried doing this</p>
  
  <pre><code>//Router.js
  import React, { Component } from 'react';
  import {StackNavigator} from 'react-navigation';
  import { AppRegistry } from 'react-native';
  import Home from './Home';
  
  let Router = 
  {
    Home: {screen: Home, screenProps:"hello"},
  }
  
  const Navigator = StackNavigator(Router);
  const nav = &lt;Navigator screenProps="hello" /&gt;
  export default nav;
  </code></pre>
  
  <p>But that caused this error</p>
  
  <blockquote>
    <p>Element type is invalid: expected a string (for built-in components)
    or a class/function (for composite components) but got: object.</p>
  </blockquote>
  
  <p>So how do I pass custom screen properties over to my Home screen from the Router file?</p>