Feature ngxcb allow overwrite

Added an overwrite option to the ngxcb script for nginx users.
Also made it default to reload nginx configuration on the ngxen and ngxdis scripts. Added a -q flag for use in scripting to avoid double reloads.

I attached an image as an example of a user
![screenshot from 2014-10-01 14 53 15](https://cloud.githubusercontent.com/assets/681226/4475314/fbdd10f4-496a-11e4-9799-c9cda70a1ee9.png)
 not being able to overwrite a certain server block. 
The problem I had specifically is installing hhvm after the first provision, and wanted to run ngxcb again and overwrite my old block quickly, this didn't work without removing the symlink and server block it points to