BUG: avoid leaking collection when calling getDisplayableManagers from python

Moved the collection into the parameter list so that it doesn't
lead to a leak when used via python.
ENH: provide SetNthFiducialPosition methods

Mirror the GetNthFiducialPosition wrapper. Added the test
into the CMake simple tests and extended it to test
these wrappers.
ENH: add tests for scene view restore

Test a simple case with one list, and then with two and a third
that's not restored.