Update class_receiveDataThread.py

Modified code so that clients send out their inventory lists with the the objects with the most proof of work first. The purpose is to ensure that a small minority of users contributing a relatively low amount of computational resources will not be able to DOS the network because their low proof of work messages are likely to be the last ones delivered and the first ones delayed past object expiration, as discussed here: https://bitmessage.org/forum/index.php?topic=4067.150