Added handling for the custom config directories

This allows config files to exist in a predefined location that should be relative to the webroot, those config files are removed and replaced with the news ones on site install. 

The hash in the drupal_lamp.json would look like
```
"config" : {
  "active": "/assets/example/files/config/active",
  "staging": "/assets/example/files/config/staging"
}
```
This should resolve: newmediadenver/drupal-lamp#107