implement chunk logs

Slightly tricky as they are not normal UUIDBased logs, but are instead maps
from (uuid, chunksize) to chunkcount.

This commit was sponsored by Frank Thomas.

Remote/Helper/Chunked.hs

@@ -9,12 +9,11 @@ module Remote.Helper.Chunked where
 
 import Utility.DataUnits
 import Types.Remote
+import Logs.Chunk.Pure (ChunkSize)
 
 import qualified Data.Map as M
 import Data.Int
 
-type ChunkSize = Int64
-
 data ChunkConfig
 	= NoChunks
 	| UnpaddedChunks ChunkSize