Search for top 10 matched faces

Currently we do this in `upload-photo`:

``` const faceLookups = response.FaceDetails.map((faceRecord) => {
return searchFacesByCroppedImage(faceRecord, buffer)
.then(response => {
if (!response.FaceMatches.length) {
return null;
}

if (response.FaceMatches.length > 0) {
return response.FaceMatches[0].Face.FaceId;
}
```

It would be goot to instead get the top 10 face matches and look up the user records (with a batched query) and then return all those faces in our calculation of what action to attach to a photo. Possible cases:

* One of the faces is yours, but not the first face
* There may be multiple users that have faces similar to your friends, display a grid of friends faces and tap the right one

We may want to reduce the number of face matches by using GeoIP or similair as a follow up change.