Support volume reconstruction of color images

The volume reconstructor works for color images, but the output is hardcoded to be grayscale. Need to make vtkPasteSliceIntoVolume::ResetOutput.configurable.

See discussion here:
https://www.assembla.com/spaces/plus/messages/4964273#comment_4990023

Migrated from https://app.assembla.com/spaces/plus/tickets/977/details