REFAC: Make getters for geometry data const

Source/Geometry/Analytic/imstkAnalyticalGeometry.cpp

Source/Geometry/Analytic/imstkAnalyticalGeometry.h

Source/Geometry/Analytic/imstkCapsule.cpp

Source/Geometry/Analytic/imstkCapsule.h

Source/Geometry/Analytic/imstkCube.cpp

Source/Geometry/Analytic/imstkCube.h

Source/Geometry/Analytic/imstkCylinder.cpp

Source/Geometry/Analytic/imstkCylinder.h

Source/Geometry/Analytic/imstkPlane.cpp

Source/Geometry/Analytic/imstkPlane.h

Source/Geometry/Analytic/imstkSphere.cpp

Source/Geometry/Analytic/imstkSphere.h

Source/Geometry/Decal/imstkDecalPool.h

Source/Geometry/Mesh/imstkImageData.cpp

Source/Geometry/Mesh/imstkImageData.h

Source/Geometry/Mesh/imstkPointSet.cpp

Source/Geometry/Mesh/imstkPointSet.h

Source/Geometry/Particles/imstkRenderParticles.h

Source/Geometry/imstkGeometry.h