Provide metaclass that forces save after new XBlock initialization

@cpennington @ormsbee @dianakhuang 

MetaclassCount += 1

For local testing, check out branch sarina/update-xblock-version on edx-platform. I've tested and verified - this does fix the Lyla Problem. However, Cale, could you please explain more why this is the issue so we can decide whether or not this is the truly correct solution to the problem?