Allow focal point to be configured by API

Currently it can only be set from the CMP UI which makes an API call to

PUT https://cmp.optimizely.com/api/v3/library/image/<id> with the body:

{ "focal_point": { "x": <value>, "y": <value> } }

The DAM API endpoint https://docs.developers.optimizely.com/content-marketing-platform/reference/patch_images-id should allow us to send this as well.