CLI Deploy: When pulling, automatically split my step code out into files

[josephjclark]

Whenever I pull a project with open pull, the CLI should split all steps out into their own files, nice and neatly on the filesystems.

It's very hard for me to understand why we wouldn't just do this. The code is too hard to edit in-line in the yaml. And for large workflows its hard to find the code.

We should use a simple convention to extract the steps somewhere nice and tidily.

I should be able to do like --no-code-splitting to disable this behaviour.