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