PHP-1063: Refactor cursor logic to follow MongoCommandCursor

https://jira.mongodb.org/browse/PHP-1063
Yes. This function just runs the query. If the query fails due to an exception *OR* it works, it returns. Error checking for that is later. If there is no success, and no exception, the extra check for command error values is checked, and if that is errormatic, another exception is thrown. There are no other options possible here.