Clarified meaning of test by removing assertion that we never even get to.
Added MongoConnection.receiveMessage to that we can support exhaust flag on cursors.
Added MongoServerBinding.isClosed() method, for consistency
Added helper implementations of MongoAsyncConnection and MongoSyncConnection to support delayed connection closing
JAVA-808: Added support for the exhaust flag on queries.  This was a bit tricky, but it handles all the edge cases, including making sure that we exhaust the responses when the cursor is closed, even if the user of the cursor did not.