feat(command-deploy): allow support for deploying by site name

[tinfoil-knight]

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Summary

Fixes #3033
Fixes #157

Currently deploying a specific directory to a site on netlify requires looking up the site id and providing it as netlify deploy --site <very-long-id>. Site Ids aren't very memorizable or readable.

This PR adds support for deploying sites by their names like netlify deploy --site my-first-site.

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[erezrokah]

🚀 Another great PR, @tinfoil-knight ❤️