Optimized Feed Controllers

Optimized and removed duplicate code.

Now thanks to `Controller_Feed_Base::_term` and `Controller_Feed_Base::_tag` __typical action__ is very clean and small :)

```php
	/**
	 * Get a list of pages with a specific term
	 *
	 * @since  1.1.0
	 *
	 * @uses  Controller_Feed_Base::_term
	 */
	public function action_term()
	{
		parent::_term();
	}
```

__Note:__ `Controller_Feeds_Blog` extends `Controller_Feeds_Base` and `Controller_Feeds_Page` extends `Controller_Feeds_Base`, not `Controller_Feeds_Template`