website

The URL is currently often placed in the description. This pull request adds a separate element for the website. 

```
$ ./whatweb -I lighttpd
WhatWeb Plugin Information
Searching for lighttpd
--------------------------------------------------------------------------------
Plugin Name               Details
lighttpd
	Author:              Brendan Coles <bcoles@gmail.com>
	Version:             0.3
	Passive function:    Yes
	Aggressive function: No
	Version detection:   No
	Description: 
	Lightweight open-source web server. 
	Website:             http://www.lighttpd.net/

--------------------------------------------------------------------------------
1 plugins found
```
As long as the URL is in the description (aka 'website' is missing) the output is as usual.