Correct doc blocks according to cs guidelines

Follow up on https://github.com/cakephp/cakephp/issues/3307#issuecomment-47212456

Also removed empty lines at the beginning of doc blocks. And shortened redundant `@var foo ...`.

This would allow further merge conflicts in the future, as currently, the "former" way will be introduced again in 3.0 now otherwise.
For example https://github.com/cakephp/cakephp/pull/3855/files#diff-b3d2ec2bff2ae851eb8184dd1d4ab9b9R294

If done right after https://github.com/cakephp/cakephp/pull/3855 (and all other branch merges) now, the merge conflicts should be minimal and easy to resolve.
Please confirm.