Add Android Place Photos Support

[thomasw]

As discussed in https://github.com/tolu360/react-native-google-places/issues/149#issuecomment-400719161 (with some slight modifications), this adds the following Google Place Photo API wrappers for android:

> RNGooglePlaces.getPlacePhotosMetadata(placeID)
[{
  placeId: '...',
  photoId: '...',
  attributions: '...',
  maxWidth: ...,
  maxHeight: ....
},
...
]

// Same as above, but it saves all the images to disk and returns a uri for each.
> RNGooglePlaces.getPlacePhotos(placeID)
[{
  placeId: '...',
  photoId: '...',
  attributions: '...'
  maxWidth: ...,
  maxHeight: ...,
  uri: 'file://...'
},
...
]

> RNGooglePlaces.getPlacePhoto(placePhotoMeta)
'file://...'

> RNGooglePlaces.getScaledPlacePhoto(placePhotoMeta, height, width)
'file://...'

[devlinb]

Any chance of this getting merged? This is great functionality that I'd love to see added!