Add tombstone file prior to localnet directory deletion

[Mario Fortier]

This is for better UX in case someone has a terminal open on a localnet directory that was deleted.

When init-localnet create a new localnet, put a tombstone file in the deleted directory (which might not be deleted if there is still a filesystem link to it).

If the tombstone is present when a new script starts, then fail the script or find a way to get the user into the proper new localnet directory.

[Mario Fortier]

Solution was just to make sure the init-localnet script can't be called under publish_output/localnet directory or child (the tombstone idea was not feasible).