add linear solver interface for dense matrix and and Lis

This request includes the following changes under MathLib/LinAlg

• delete SystemOfLinearEquations classes and instead use Solver classes which takes a matrix and vectors as input, e.g. Solvers/DenseDirectLinearSolver.h
• extend dense matrix interface and linear solver
• add Lis version implemenation in MathLib/LinAlg/Lis
• add a new test case for Vector, Matrix and LinearSolver