New module: require plugins

[mallorydxw]

There should be a simple way to check that required plugins are installed.

i.e.:

<?php

namespace Dxw\MyTheme;

class CheckPlugins extends \Dxw\Iguana\Extras\CheckPlugins
{
    protected $plugins = [
        'advanced-custom-fields-pro',
    ];
}

<?php
$registrar->addInstance(new \Dxw\MyTheme\CheckPlugins());

This should either:

• Activate the plugin, and show an error when the user tries to deactivate it, or
• Show an error in wp-admin so long as the plugin is not activated, with a button to activate the plugin(s)