batch_write_incremental / old API completed

RUBY-676

This is the major commit for this feature with the old API.  The new write commands will be used with compatible servers.  Write concern w:0 uses the old write operations.  The write commands go to the primary since they aren't on the SECONDARY_OK_COMMANDS list.  There is a new faster batch_write_incremental that uses BSON::Grow for the new insert command.

As of nightly 2013-10-16 and 2.5.3 release, update top:0 only updates one document.  So tests are filtered out for features like this that are not yet complete on the server or where the server response is not yet complete.