Share open graph android

try this on both iOS and Android :
```
facebookConnectPlugin.showDialog({
  method: 'share_open_graph',
action_type: 'og:share',
action_properties: JSON.stringify({
    object: "http://og.mateprofiler.com/en/app.html"
  })
});
```

on iOS you have the thumbnail, currently on Android it is processed like share.
Commit allow to use share_open_graph, but the response remains something with keys like com.facebook.platform.extra.POST_ID instead of only post_id on ios or javascript sdk

spaces `if (previewPropertyName == null) {`