Add a documentation module that contains information keys

Eventually all vtkInformationKeys should be added to this module.  This
commit only gets some of the more common ones.

Change-Id: Ic1c116b190c20f108fc064d2dad1ee516ebf7626
Merge topic 'DOC_add_information_key_module' into master

25fd4c5f Add a documentation module that contains information keys