Objects: Ability to create directories

[alexfreska]

Implement something similar to the S3 behaviour outlined below.

https://docs.aws.amazon.com/AmazonS3/latest/userguide/using-folders.html

When you use the Amazon S3 console to create a folder, Amazon S3 creates a 0-byte object with a key that's set to the folder name that you provided. For example, if you create a folder named photos in your bucket, the Amazon S3 console creates a 0-byte object with the key photos/. The console creates this object to support the idea of folders.