Progress on message parsing, added mutable array to ActivePeer representing the pieces the peer has.

Modified
  -src/BEncode.hs
    -Refactoring
  -src/Metainfo.hs
    -Added infoPieceLength and infoPieceCount convenience functions.
  -src/Peer.hs
    -Added pr prefix to records (this will spread to other datatypes as well soon).
    -Added prPieces record, which is an IOUArray.
  -src/Protocol.hs
    -Perform actual partitioning of message payloads using slices.
    -Fixed bug in how msgId was parsed.
  -src/SocketManager.hs
    -Reintroduced MVar (which never actually gets put'd).
  -src/Torrent.hs
    -Placeholders for message-logic are in place (fleshed out processMessage).
  -src/TorrentManager.hs
    -Removed accepting of new connections temporarily
    -Reassessing the role of this file in the application.