Add number of objects or sum of unknown sample weights to region pickle output

[morriscb]

In order to combine the clustering-zs of a set of sub bins into a large bin we need to know how many objects were used in the clustering-z and or what the sum of their weights were.

This issue adds this data to the region pickle file that is an option output of pdf_maker.py.

[morriscb]

Added initial version of the region_weights to the output pickle. Still need to clean up and unittest code.