Allow other plugins to provide plugin data too

The filter should return an array, this could be an empty array or an array containing as a minimum the below for each plugin, obviously with data for the provides/depends key where applicable:
```php
array(
	'plugin-dir/file.php' => array(
		'Name' => 'Plugin name',
		'Provides' => '',
		'Depends' => '',
	)
)
```
Change filter setup
Merge pull request #33 from jrfnl/Add-plugin-data-provider-filter

Allow other plugins to provide plugin data too