KW00001404: Remove attribute designation from appending logic

vtkAppendFilter and other appending classes would first use active
attribute status, if any, to determine how to append data arrays from
the inputs, and use names of arrays only secondarily to decide which
arrays to append. This could lead to unexpected behavior depending on
which data arrays were made active attributes by, say, an upstream
filter.

This patch changes the intersection logic in
vtkDataSetAttributes::FieldList to consider only array names and
ignores active attribute status.

In the case where the data arrays designated as a particular attribute
in all the inputs have the same name, then the output array with that
name is set to the active attribute in the output.

Change-Id: I75d409543bf5f95683d62555d37df04afe8b8d0f