[RFC] Check if an alire project already exists in directory skip project questions

[AdaOrbit]

Currently when running alr init foo alire asks a lot of questions about the crate like title, description, license, etc and creates the project directory with foo/alire.toml. But when running the same command twice alire asks all the questions again just to fail at the end with

warn: foo/alire.toml already exists.
error: Cannot create 'foo/alire.toml'

This is somewhat annoying since you spend some time to fill out all the questions and get an error at the end that could have been checked before.

Proposal: check beforehand if an alire project already exists. If if does: don't even bother to ask the developer for all the crate descriptions.