Added phpdoc_separation fixer

The idea here is to go from:

```php
    /**
     * @param EngineInterface $templating
     * @return void
     */
```

to 

```php
    /**
     * @param EngineInterface $templating
     *
     * @return void
     */
```
When we need to add a newline we add simply `\n`. Yes, it is a bug on current version.

When we dont need to change newline - don't change it introducing new bug.