git-annex sim command is working

Had to add Read instances to Key and NumCopies and some other similar
types. I only expect to use those in serializing a sim. Of course, this
risks that implementation changes break reading old data. For a sim,
that would not be a big problem.

Annex/Locations.hs

@@ -108,6 +108,7 @@ module Annex.Locations (
 	gitAnnexSshDir,
 	gitAnnexRemotesDir,
 	gitAnnexAssistantDefaultDir,
+	gitAnnexSimDir,
 	HashLevels(..),
 	hashDirMixed,
 	hashDirLower,
@@ -675,6 +676,9 @@ gitAnnexRemotesDir r =
 gitAnnexAssistantDefaultDir :: FilePath
 gitAnnexAssistantDefaultDir = "annex"
 
+gitAnnexSimDir :: Git.Repo -> RawFilePath
+gitAnnexSimDir r = P.addTrailingPathSeparator $ gitAnnexDir r P.</> "sim"
+
 {- Sanitizes a String that will be used as part of a Key's keyName,
  - dealing with characters that cause problems.
  -