BUG: Add missing ITK_OVERRIDE to ITKImageeSources module.

Change-Id: I5ae748185e0ef67b3169a5311b5f643987166e2f
BUG: Remove GaussianImageSource members shadowing GenerateImageSource.

These members are already defined in GenerateImageSource (the base class),
and they should not be repeated in GaussianImageSource.

Change-Id: I287c2011b5a6ab0ec755ce211919de6167ff428a
STYLE: Style fixes to ITKImageSources module.

Change-Id: Iad7874ecacec81ebe19a2d39f7809b59ee2576e0
BUG: GaussianSpatialFunction and GaborImageSource use SpacePrecisionType.

Change-Id: Idd8e90e9160375c60df233a9efca28e88152c501
Merge topic 'ImageSourcesFixes'

e8045bf1 BUG: GaussianSpatialFunction and GaborImageSource use SpacePrecisionType.
a11606a8 STYLE: Style fixes to ITKImageSources module.
cc48b577 BUG: Remove GaussianImageSource members shadowing GenerateImageSource.
3fd28cc3 BUG: Add missing ITK_OVERRIDE to ITKImageeSources module.