Implementing delete function for photo

- Implement delete function for photo; deleting photo remove database record and file on aws S3.
- Implement function to assign front_page_photo to kitchen
Be careful with this code.  You're assuming everything will work.  What happens if `@photo.remove_picture!` succeeds but `@photo.destroy` fails?  What happens if `@photo.remove_picture!` fails but `@photo.destroy` succeeds?

In either case, your application will be in an inconsistent state.

Also, per the documentation, calling `Photo#destroy` will automatically call `remove_picture!`.  See https://github.com/carrierwaveuploader/carrierwave#skipping-activerecord-callbacks.