This fixes a few issues with how "prominent values" were handled.

1. `vtkSMRepresentationProxy::GetProminentValuesInformation` always
   looked are represented data and never and it's input's data. That is
   different from how info for non-prominent values is handled.
   When coloring etc, we first look at the array range for the array
   from input, if present and then from represented data if the array
   was not present on the input. This was causing the molecule
   representation to not have any atomic numbers related information on
   creation. fixed that.

2. `vtkPVProminentValuesInformation` didn't have correct code in
   `CopyFromObject`. It was just a copy-paste from vtkPVDataInformation
   which didn't make sense for vtkPVProminentValuesInformation. Fixed
   that.