Support mutiple apps inside the vm

I'd like to propose a slightly modified layout for hosting several apps inside the vm by adding a www directory mounted on /var/www inside the vm. The resulting layout would be
```
- vagrant
- www
-- backend
-- frontend
-- ...
- Vagrantfile
```

inside the vm the result will be

```
- /var/www
-- backend
-- frontend
```

What do you think? @ricfrank @ftassi 