title: React Navigation pass props in TabNavigator
body: <p>I have props what are loaded from the server on the initial screen. I want to pass them to the rest of the tab screens. However, I have not found any examples online. I know of the screenProps, but have no idea how to set it up. All methods I have tried, have resulted in errors.</p>
  
  <pre><code>const EProj = TabNavigator({
    Home: { screen: HomeScreen },
    Map: { screen: MapG },
    Login: { screen: Login },
    Profile: { screen: Profile },
  }, {
    tabBarPosition: 'bottom',
    animationEnabled: true,
    tabBarOptions: {
      activeTintColor: '#1abc9c',
    },
  });
  </code></pre>
  
  <p>This is my screen setup. Where should I place the screenProps?</p>
  
  <pre><code>&lt;EProj
    screenProps={cats}
  /&gt;
  </code></pre>
  
  <p>Any good examples how to set this up would be helpful. Thanks in advance.</p>
  
  <p>HomeScreen setup:</p>
  
  <pre><code>class HomeScreen extends React.Component {
    static navigationOptions = {
      tabBarLabel: 'Home',
    };
  
  ...
  
    componentWillMount(){
      console.log("Starting to load assets from server!");
      this.onLoadCats(); /*starts asset loading*/
    }
  
    render() {
      return (
        &lt;View style={styles.container}&gt;
  
          &lt;Text&gt;Welcome to alpha 1.17 This is hard system test.&lt;/Text&gt;
          &lt;AssetsLoad catsL={this.state.catsL} /&gt;
        &lt;/View&gt;
      );
    }
  }
  </code></pre>