project: limit length of id slugs

When the CLI loads a project from lightning, we take the name and convert it to a url-safe slug:
```
let-s-croak-us-some-toads
```

This slug probably doesn't need to be more than say 10 chars long. If 10 chars doesn't give us a locally unique slug, we can use more until we have uniqueness. All the information we need is available