Make CLI generate .platform configuration files when importing a project

[GuGuss]

It should ask couple of questions like: "toolstack"...

[Kazanir]

I think we want to wrap this into a new set of commands starting with app: that can manage applications as individual units (and re-factor the other parts of the CLI to contemplate the idea of multiple applications and treat their application roots properly...)

This sort of thing would allow us to have platform get instantiate a new project and ask the questions for a single app, but also allow platform app:add to do the same to add a second application to an existing project...going to gather feedback on this next week.