WIP Update to remove Enum_Context and clean up tests to match new

proposal namespace.  Implemented the result of all of the pull
 operations as a named tuple with three parts, instances/paths,
 end_of_sequence, enumeration_context

Cleans up most of the documentation for OpenEnumerateInstances and
PullInstancesWithPath.  Note that there are a
couple of issues around MaxObjectCount to be worked out.

This is only a WIP

Add INSTANCEPATH as IRETURNVALUE child in tupleparse.py

Doc modifications per Andy's comments

Implements all of the operations.  Add a number of tests against pegasus for OpenEnumInstances and OpenEnumPaths

This adds the remaining operations to cim_operations. The result of all
of the pull operations is a named tuple.  The documentation is update
for OpenEnumerationInstances and PullInstancesWithPath. There is still
work including a)add documentation to the other operations once we agree
on the documentation for the OpenEnum, etc. b)Add tests against pegasus
c) get the mock working.