CHECK_ERROR_MSG and CHECK_WARNING_MSG are used to check the
content of error and warning messages. Error and warning code is often
overlooked during testing. Over the years, these two macros have been
refined to increase their utility. Tests that use the macros defined
their own interpretations. Three different API's have been used in the
macros.

This patch replaces the CHECK_ERROR_MSG and CHECK_WARNING_MSG macros
with methods for vtkTest::ErrorObserver.  All tests that used the
CHECK macros in one form or another have been updated to use the
CheckErrorMessage and CheckWarningMessage methods.