Update sample differencing DFXML: Change file contents

Signed-off-by: Alex Nelson <a.nelson@prometheuscomputing.com>
Test fileobject count in cat output

Signed-off-by: Alex Nelson <a.nelson@prometheuscomputing.com>
cat_fileobjects.py: Add a debug flag

Signed-off-by: Alex Nelson <a.nelson@prometheuscomputing.com>
idifference: Test text report and fileobject tally

Unfortunately, this test shows the fileobjects aren't being generated
anymore.
Python, unit tests: Add XMLNS-by-default logic

* dfxml: Added an ElementTree tostring() function wrapper that removes
  redundant namespace declarations.  This includes extra unit tests for
  a new regular expression.
* idifference: Corrected a fileobject counting bug (where a counter
  reset was forgotten).
* idifference, icat: Added some XML namespace handling logic, found
  necessary but missed until the last unit test updates.

Signed-off-by: Alex Nelson <a.nelson@prometheuscomputing.com>