Replacing vtkMath::Random with vtkMinimalStandardRandomSequence

Examples not done because they need external modules:

./Cxx/Points/PoissonExtractSurface.cxx
./Cxx/Points/PowercrustExtractSurface.cxx
./Cxx/Visualization/ExtrudePolyDataAlongLine.cxx

Seed is set for vtkBrownianPoints using vtkMath::RandomSeed():

./Cxx/Utilities/BrownianPoints.cxx