[Run2_2017] V16 weightProducer Fixes for Summer16MiniAODv3 samples

Created by: aperloff

This commit:

1. Adds new neff dictionaries to condorSub
2. Adds new getWeightProducer lines for the Summer16MiniAODv3 datasets
3. Fixes the format of the Summer16MiniAODv2 datasets with negative weights
4. Adds new unit tests
5. Adds/updates some cross sections