Only save a project if its creation is entirely successful

[chasefleming]

Closes #1531

This creates the whole project in a system temporary directory until the entire project is successfully created, otherwise it is destroyed. Upon successful creation, it moves it out of the temp directory and into the target directory.

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[jribbink]

Awesome! Just some nits about error handling mostly

[jribbink]

LGTM, tested and works.

If we can just cleanup printing the temp paths (maybe just exclude them, reference them as relative instead of absolute, or print the target paths instead) that would be awesome: