Adding copyright header to sparse matric unit tests source files.

src/UnitTests/Matrices/SparseMatrixTest_CSR.cpp

src/UnitTests/Matrices/SparseMatrixTest_CSR.cu

src/UnitTests/Matrices/SparseMatrixTest_Ellpack.cpp

src/UnitTests/Matrices/SparseMatrixTest_Ellpack.cu

src/UnitTests/Matrices/SparseMatrixTest_SlicedEllpack.cpp

src/UnitTests/Matrices/SparseMatrixTest_SlicedEllpack.cu

src/UnitTests/Matrices/SymmetricSparseMatrixTest.hpp