DOC: Clean up comments in NiftiImageIO, for better Doxygen compatibility

Change-Id: I8441f6c31a07f7d17c9b89b014ff556bc542505a
STYLE: Remove unused typedefs from AlgorithmsPrintTests

These were left over from before AlgorithmsPrintTest was split into
separate files.

Change-Id: I04865517dfb17585b6975f25408d16642109fbe0
BUG: Fix improper usage of VoronoiSegmentationRGBImageFilter

VoronoiSegmentationRGBImageFilter requires a PixelType with 3 components.
Fixing this also resolves a compiler warning.

Stronger concept checking should also be added in the future to ensure
this usage: bug ITK-3231.

Change-Id: I0d624c8d4be9f3bedc962a5027714e90e54f693d
Merge topic 'NiftiComments'

5e239fc DOC: Clean up comments in NiftiImageIO, for better Doxygen compatibility
Merge topic 'AlgorithmsPrintTest'

194f2f0 BUG: Fix improper usage of VoronoiSegmentationRGBImageFilter
18ab102 STYLE: Remove unused typedefs from AlgorithmsPrintTests