Add support for Eclipse Clean Up

From my understanding Spotless uses `org.eclipse.jdt:org.eclipse.jdt.core` to do formatting with Eclipse. Currently this only provides whitespace changes, but Eclipse itself also has `Clean Up` which makes code changes. I think this functionality is provided by the `org.eclipse.jdt:org.eclipse.jdt.ui` package. Would it be possible to also add this functionality to Spotless?