Add ability to totally release memory in Python

People think that ResetSession resets memory in Python sessions. This is not true, as described by Mathieu in https://discourse.paraview.org/t/resetsession-not-clearing-memory/15975/8. Please create/add ResetSessionAndCleanNameSpace to simple.py. The primary place I see this issue is where users will wrap a trace with a for loop and itterate over numerous datasets. This will frequently crash, as memory grows and grows. We need a way to reset the pipeline to virgin/clean/freed memory.