SSL Certs

Implemented SSL certificate configuration for apache and nginx.

Example of vhost with ssl (remove ssl_cert and ssl_key options if you want to use the self signed certificate generated automatically by Protobox):
```
  vhosts:
    - name: app
      servername: app.dev
      serveraliases:
        - 'www.app.dev'
      docroot: /srv/www/web/protobox
      port: '443'
      setenv:
        - 'APP_ENV dev'
      override:
        - All
      ssl: 1
      ssl_cert: '/srv/www/data/ssl/server.crt'
      ssl_key: '/srv/www/data/ssl/server.key'
```
More information about this feature: https://github.com/protobox/protobox/issues/50