simplify process_stock and break up create_models_for_stock_report
simplify process_stock and break up create_models_for_stock_report

also try to use fully descriptive names for variables

qedsoftware/commcare-hq,qedsoftware/commcare-hq,dimagi/commcare-hq,dimagi/commcare-hq,dimagi/commcare-hq,qedsoftware/commcare-hq,dimagi/commcare-hq,qedsoftware/commcare-hq,dimagi/commcare-hq,qedsoftware/commcare-hq