Fixes

  * Limited the number of requests that can be outstanding with a single peer
  * Moved ClassifiedPeers into the QuartzTorrent namespace
  * Added simple memory profiling class, and screen on curses downloader to display memory info
  * Fixed memory leak where piece manager request metadata for pending requests was not being deleted
  * Fixed soft memory leak where if the upload rate for a given peer was not queried the number of samples
    for the rate keeps growing indefinitely
  * Added safeguards around writing too many characters into the reactor's event pipe. Without these there is
    a low probability of a deadlock