Improve Stream Notification support

When a Stream Context contains a "notification" parameter we'll send
  notification_code = MONGO_STREAM_NOTIFY_TYPE_IO_INIT
  message_code =
    MONGO_STREAM_NOTIFY_IO_READ
    MONGO_STREAM_NOTIFY_IO_WRITE
  bytes_max = How much we are about to read/write total

During the read/write we'll send incremental notification per chunk
  notification_code = MONGO_STREAM_NOTIFY_IO_PROGRESS
  bytes_max = how much we are about to read/write total
  bytes_transferred = how much we have read/written so far

Upon completion we'll send
  notification_code = MONGO_STREAM_NOTIFY_IO_COMPLETED
  bytes_max = how much we are about to read/write total
  bytes_transferred = how much we have read/written total

We'll also send notifications for actions (CRUD/KILL/GETMORE)
  notification_code = MONGO_STREAM_NOTIFY_TYPE_LOG
  message = JSON serialized array containing several different keys
    "server" (array): Always available
    "type" (int): MONGO_NODE_xxx
    "max_bson_size" (int): Maximum BSON Size
    "max_message_size" (int): Maximum BSON Message Size
    "request_id" (int): The request number
    See below for more info about each action

  message_code =
    MONGO_STREAM_NOTIFY_LOG_INSERT
      Additional "message" JSON keys:
      "document" (array): The document being inserted
      "options" (array): Insert options (WriteConcern etc..)

    MONGO_STREAM_NOTIFY_LOG_QUERY
      Additional "message" JSON keys:
      "query" (array): Query to execute
        NOTE: Massaged for mongos
      "info" (array):
        "request_id": Request number
        "skip": numberToSkip
        "limit": numberToReturn
        "options": bit vector of query options (slaveOk/tailable etc..)
        "cursor_id": (always 0)

    MONGO_STREAM_NOTIFY_LOG_UPDATE
      Additional "message" JSON keys:
      "criteria": Search query
      "newobj": Modified object to store
      "options" (array): All options passed to the command
      "info" (array):
        "namespace": Document namespace to update
        "flags": bit vector of update options (upsert/multi etc..)
    MONGO_STREAM_NOTIFY_LOG_DELETE
        Same as LOG_UPDATE, except for "newobj"

    MONGO_STREAM_NOTIFY_LOG_GETMORE
        "info" (array):
            "request_id": Request number
            "cursor_id": Cursor ID to ask for more data

    MONGO_STREAM_NOTIFY_LOG_KILLCURSOR
        "info" (array):
            "cursor_id": Cursor ID to kill

    MONGO_STREAM_NOTIFY_LOG_BATCHINSERT
      "docs": array of documents to insert
      "options" (array): All options passed to the command
      "info" (array):
        "flags": bit vector of update options (upsert/multi etc..)

    In addition, all READ operations also return:
    message_code=MONGO_STREAM_NOTIFY_LOG_RESPONSE_HEADER
        "query": The query we got results for
        "info":
            send_request_id": Request number
            "cursor_id": The cursor ID this query created/operates on
            "recv_request_id": The Request ID
            "recv_response_to": The Request ID the server is reply to
            "recv_opcode": Request Type (OP_XXX)
            "flag": Any previously set flags on the serverbbb
            "start": Where this cursor is starting from
An example script using the new Stream Notification system

The script prints out a "wget style" progress notification when
reading/writing data over the socket - and how long it took.

It also prints out some server and cursor information, along with the
command (count) and query (empty) being executed.