Makes phpcollection/phpcollection redundant

[jurgenhaas]

Fixes #188

[GenieTim]

Thank you very much for this contribution!
If you want, you can use composer fix-cs to automatically fix the code style issues

[jurgenhaas]

Hmm, that was kind of a challenge. I cloned the repository, ran composer update and then called composer fix-cs which failed with error messages like this:

Call to undefined function grapheme_strlen() in /drupal/vendor/symplify/easy-coding-standard/vendor/symfony/string/UnicodeString.php:171

Not sure, why that happened but I replaced grapheme_strlen with mb_strlen and then the tests worked.

I then realized that the code quality of those classes was really terribly. I went through a couple of iterations and then just had some errors left from classes, that had been there before:

Property GitElephant\Objects\Diff\DiffChunk::$originStartLine (int) does not accept string.

I fixed them as well, hoping this is not breaking anything. But now it seems that the testbot is running into timeouts. Can you probably force a re-test?