installation frontend javascript bugfix - win/xampp

Windows only issue:

Using str_replace to replace **backslashes** to **forward-slashes** in case of SQLite. 
Windows PHP understands forward slashes correctly. This is because of potential javascript error while setting something like this:
```javascript
$('#config_db_name').val('C:\xampp\db\wolf.sq3')
```
the `\xam` part of the above string is treated as an escaped **octal code** in string and generates browser syntax error.

Converting path string to use forward slashes resolves this resulting in:

```javascript
$('#config_db_name').val('C:/xampp/db/wolf.sq3')
```

Additionaly, removed `#config_db_driver` **onchange** property which called non-existing fuction `db_driver_change` - this also generated browser errors.