Implement copyDirs parameter, similar to copyFiles

Should recursively copy directory content to destination.

http://forum.rejectedsoftware.com/groups/rejectedsoftware.dub/thread/4875/

Working ok on dub build. Not sure about visuald/monod generators.

I've never seen dirEntries returning ".", sure it's needs?
http://dpaste.dzfl.pl/fa97e9925d67