Wordpress Plugin

Plugin that iterates (Apache for now) configured vhosts and looks for WordPress content. If found, it attempts to report WordPress version and plugins versions:

```
  "webapps": {
    "wordpress": {
      "wordpress.example.com": {
        "path": "/srv/wordpress_sample/wp-config.php",
        "version": "3.8.1",
        "plugins": {
          "Akismet": {
            "version": "2.5.9"
          }
        }
      }
    }
  }
```

Concerns:
* Could cause too much filesystem activity. Currently, plugin scans entire vhost directory for `wp-config.php` with some configured standard exclude directories (`.git`, `images`, etc.). Needs better recursive logic.
* Plugins scan looks at each plugin directory and scans all files in the top level of this directory looking for required WordPress plug-in metadata. Unfortunately, there is no convention on what file it is found in. However, once `name` and `version` are found, it stops scanning that file and that plug-in.
* If multiple vhosts are configured and point to the same docroot with WordPress, this will cause multiple entries in the `webapps/wordpress` namespace because it keys off of vhost name.