ADD : PointSetDensity Function & related tests

Code/BasicFilters/otbPointSetDensityFunction.h

Code/BasicFilters/otbPointSetDensityFunction.txx

Code/BasicFilters/otbPointSetFunction.h

Code/BasicFilters/otbPointSetFunction.txx

Testing/Code/BasicFilters/CMakeLists.txt

Testing/Code/BasicFilters/otbBasicFiltersTests11.cxx

Testing/Code/BasicFilters/otbCountImageFilterTest.cxx

Testing/Code/BasicFilters/otbPointSetDensityFunctionNew.cxx

Testing/Code/BasicFilters/otbPointSetDensityFunctionTest.cxx

Testing/Code/BasicFilters/otbPointSetFunctionNew.cxx