Cleanup use statements

We definitely need a sniff for this.
Maybe one can wrap my detection lib here in some sort of "Use" sniff.

I also found 30+ more issues with https://github.com/dereuromark/cakephp-codesniffer/tree/3.0#cleanup and

    .\bin\cake CodeSniffer.cleanup unused_use /path/to/cake3/src/

The tests folder I didnt even look into yet.