Reorganize slightly integration descriptors

src/scheme/IntegrationMethodType.hpp

src/scheme/PolynomialReconstruction.cpp

src/scheme/PolynomialReconstructionDescriptor.hpp

src/scheme/test_reconstruction.cpp

tests/test_PolynomialReconstruction.cpp

tests/test_PolynomialReconstructionDescriptor.cpp

tests/test_QuadraticPolynomialReconstruction.cpp