Add --overwrite to stellar contract init

[fnando]

What problem does your feature solve?

Templates change. Maybe you want to pull in all new changes, especially when using astro templates.

What would you like to see?

--overwrite can overwrite all files automatically.

What alternatives are there?

Removing files manually then running the command to install a new version of the templates.

[leighmcculloch]

This option would make the init command very destructive. The user already has tools they can use to destroy files, so the cli wouldn't be providing something significant impactful.

Also I expect a command for overwriting will be more useful to someone repeatedly starting from scratch which doesn't exactly sound like the workflow of a contract developer. It sounds like the workflow of someone testing the CLI.

What's the motivation behind adding the option?