Fix cli_installer.php

Hello, 

I tried to make change to less file as possible to ensure it won't impact the web installer.
For this reason, I need to make a few change on arguments name.

```
Usage:
======

php cli_install.php install --db_hostname localhost --db_username root --db_password pass --db_database opencart --db_driver mysqli --username admin --password admin --email youremail@example.com --agree_tnc yes --http_server http://localhost/opencart
```

I also add a new argument called `db_driver` which is `mysqli` by default.
I removed directories permission checking since the installer can handle this on its own.

Hope this merge request help you.