Removed the inheritance of DenseMatrix from MatrixBase.
Removed the inheritance relation of SparseMatrixBase to MatrixBase.
Removed the class MatrixBase.
Added a second template parameter for the index type.

Added a second template parameter for the index type to class template DenseMatrix.
DenseMatrix: added assignment operator, improved copy constructor.
Initial commit for class template GlobalDenseMatrix.
Added simple test for GlobalDenseMatrix.
Added move constructor and move assignment operator.
Changed return data type from int to bool for setValue() and addValue().