XD-293 Ensure package-info.java to all packages

- Add missing `package.info` to all the packages
- Fix/Update javadoc
- Move `org.springframework.xd.dirt.XDRuntimeException`
to `org.springframework.xd.dirt.util.XDRuntimeException`
can remove the TODO (we should defer the package move, since it will be part of larger 1.1 refactoring as mentioned in another comment)