Git clone wizard should check directory before

1. Start cloning a git repository using "File" -> "New File or Project..." -> "Import Project" -> "Git Repository Clone".
2. Enter a valid Clone URL.
3. In "Working Copy", select an existing, non-empty directory.
4. Click "Next".
   The dialog will show something like:

   fatal: destination path 'someDir' already exists and is not an empty directory.
   

Creator should check the directory and, if needed, inform the user already before they click "Next".