reorganize numcopies code (no behavior changes)

Move stuff into Logs.NumCopies. Add a NumCopies newtype.

Better names for various serialization classes that are specific to one
thing or another.

Types/NumCopies.hs

@@ -0,0 +1,14 @@
+{- git-annex numcopies type
+ -
+ - Copyright 2014 Joey Hess <joey@kitenet.net>
+ -
+ - Licensed under the GNU GPL version 3 or higher.
+ -}
+
+module Types.NumCopies where
+
+newtype NumCopies = NumCopies Int
+	deriving (Ord, Eq)
+
+fromNumCopies :: NumCopies -> Int
+fromNumCopies (NumCopies n) = n