implement click event on MapOverlay

[ichan-mb]

Added support for clicked/tapped event on MapOverlay

Examples:

<App>
    <ClientPanel>
        <JavaScript>
            module.exports.overlayTapped = function(args) {
                console.log("overlay tapped");
            }
        </JavaScript>
        <NativeViewHost Dock="Top" Height="250">
            <MapView ux:Name="map" Zoom="14" Latitude="-6.914742" Longitude="107.609820">               
                <MapOverlay Radius="60" Type="Circle" FillColor="Red" Tapped="{overlayTapped}"
                    CenterLatitude="-6.914742" CenterLongitude="107.609820" />
            </MapView>
        </NativeViewHost>
    </ClientPanel>
</App>

This PR contains:

• [ ] Changelog
• [ ] Documentation
• [ ] Tests

[mortend]

• [x] https://travis-ci.org/github/fuse-open/fuselibs/builds/753774128