Lots of little improvements and cleanup

  - Use an excludes file instead of command line parameters for
    defining what files to exclude from a sync
  - Sync a few more things from my Documents directory that
    I consider important
  - Make sync delete things when they've been deleted in the
    source directory. This ensures that synced folders match
    the original, even when things are deleted or renamed. Hopefully
    this also reduces the chances for conflicts.