Adds a rename feature + Adds a 'stripslashes' feature

I've added a rename feature : 
```shell
virtualhost.sh --rename <site_url> <new_site_url>
```
It's been useful to me for projects with environments settings based on URL. I can easily switch between development and staging version if needed.
Ex : http://website.dev/ and http://website.staging/

I've also added a 'stripslashes' feature to avoid having slashes in the virtualhost.
This change seems out of scope unless I'm missing something…