Preserve Finder tags

[oakif]

If you add the executability tag into the rsync flags you can preserve Finder tags (I thought it would be the extended attributes tag which did this, but the rsync version which comes on macOS doesn't support that tag).

The only issue I've found is that changing the Finder tag of a file changes the corresponding extended attribute of the hardlinked node, meaning that the Finder tag updates across all of your previous backups. It's not a huge deal unless you really need to preserve Finder tag info in your previous backups.

I was going to make a pull request but decided not to because of this issue. If anyone can give advice I'd be willing to listen!