Relative Mode for vtkTemporalArrayOperatorFilter

The vtkTemporalArrayOperatorFilter now has a RelativeMode, where it uses UPDATE_TIME_STEP time as first value alongside to a TimeStepShift shifted value, instead of two static time steps.

Behavior Breaking Change

This filter was inconsistent on which input mesh and arrays were forwarded to output: Composite data used first input, while non composite used second. The forwarded data is now the one given by FirstTimeStepIndex when RelativeMode is off or by UPDATE_TIME_STEP otherwise, as Composite used to do.

Build Breaking Change

The protected variable members where moved to private. From inherited classes, please use Getter/Setter instead.