Custom scaffold templates - POC

This code adjustment and the new global config makes it possible have your own simple extended plugin or other templates if implemented for the Unit tests.

`wp scaffold plugin zombieland --author='Jaime Martinez'`

`~/.config/plugin.mustache` :
```
<?php
/*
Plugin Name: {{plugin_name}}
Version: 0.1-alpha
Description: PLUGIN DESCRIPTION HERE
Author: {{author}}
Author URI: YOUR SITE HERE
Plugin URI: PLUGIN SITE HERE
Text Domain: {{textdomain}}
Domain Path: /languages
*/
```
`wp-cli.yml` :
```
scaffold plugin:
  template_path: '/Users/jmslbam/plugin-x.mustache'
```

- [ ] CPT
- [ ] TAX
- [ ] Plugin tests
- [ ] Child theme?
- [ ] var / args?

**var / args (template_path)**
I think a per sub command `template_path` could be ok because most of the time you will only overwriting 1 or 2 templates.
Otherwise we could configure a global template_path and check which files are avialable to overwrite.