Clobers existing files

[shelane]

I ran fin composer require docksal/blt-docksal and then ran fin blt recipes:docksal:project:init. My existing docksal init and init-site commands were clobbered and replaced. My docksal.yml and docksal.env files were also replaced.

We should look at making this process a little smarter to digest what is there, add what needs to be added to the docksal.yml and docksal.env files without replacing the existing files.

At bare minimum, it should be documented that this will happen. Fortunately, it's easy enough to compare and restore from my Git repo.