add support for panHandlers={null} in Scene (#1404)
add support for panHandlers={null} in Scene (#1404)

This is very convenient to prevent the user from swiping a scene manually.
dmazin/react-native-router-flux,aksonov/react-native-router-flux,gijoehosaphat/react-native-router-flux,gijoehosaphat/react-native-router-flux,dmazin/react-native-router-flux,mcabs3/react-native-router-flux,gijoehosaphat/react-native-router-flux,charpeni/react-native-router-flux,mcabs3/react-native-router-flux,charpeni/react-native-router-flux,mcabs3/react-native-router-flux,charpeni/react-native-router-flux,Wondermall/react-native-router-flux,Wondermall/react-native-router-flux,dmazin/react-native-router-flux,Wondermall/react-native-router-flux