Escape arguments when installer invokes commands

The usage of shell: true means that no escaping is done on the arguments
passed to the commands invoked by the installer. This leads to the
installation failing if the user for example puts a space in the
username for the admin account.

Fix by escaping the arguments passed on command lines. This is
unreasonably complicated on Windows 😡.

test/create/forward_args.sh

@@ -0,0 +1,3 @@
+#!/bin/sh
+# this is how package.json bin entries forwards arguments on Linux
+exec node "$@"