Improve compatibility with other services

[JonasKruckenberg]

The current imagetools API is quite verbose and is also quite different to the ones used by popular services.
This issue aims to gather good ideas to adopt from other services and ways we might archive this.
At the very least this would entail adding shorter aliases to directives like b for background etc.
Another option would be to modularize the url parsing logic, so that we could potentially have a "Cloudinary interop package" for example.
Don't know how necessary that might be though, I'm very much looking for feedback for this issue!

There are also things that we cannot adopt as well, like having the transforms be part of a path segment (and I frankly think it goes against the semantic meaning of url path segments, but whatever)