limiting files based on metadata

Note that there is currently no caching, so
	--metadata foo=bar --metadata tag=blah
will currently read the log 2x per file.

Annex/FileMatcher.hs

@@ -83,6 +83,7 @@ parseToken checkpresent checkpreferreddir groupmap t
 			, ("inbackend", limitInBackend)
 			, ("largerthan", limitSize (>))
 			, ("smallerthan", limitSize (<))
+			, ("metadata", limitMetaData)
 			, ("inallgroup", limitInAllGroup groupmap)
 			]
   where