Implement custom reporter class

[JaZo]

Detailed description

The current implementation is based on parsing the GitLab format. It would be better if we would implement our own reporter class.

Context

PHP CS Fixer doesn't support custom reporters (see PHP-CS-Fixer/PHP-CS-Fixer#5534).

Possible implementation

Implement our own reporter class to directly push annotations to Bitbucket without piping. This would allow us to also report the violations using the built-in (default) text reporter, so you have both text output and a Bitbucket report.