Added PhpdocSeparationFixer

TODO:
* [ ] Add tests for stuff the `DocBlock` class
* [ ] Add tests for stuff the `Lines` class
* [ ] Add tests for stuff the `Annotations` class
* [ ] Fix the behaviour with some annotations like the phpunit ones...

Do we perhaps need to only separate a whitelist of annotations, and leave the rest unchanged rather than not separate a blacklist?
:+1: