Need to support nearest and linear filter for all Volume data types

[Kevin Griffin]

Need to support nearest and linear filtering (ideally cubic too) for all Volume data types. Currently nearest and linear filtering is only supported for float Volume data. Volume data of type int (uint8, uint16, int16) using anything but nearest filtering will result in an error.

[Jefferson Amstutz]

Implemented on next_release branch in 83be7d2.