[MathLib] Tool for testing GaussAlgorithm.

This tool reads a matrix, and solves a simple system of linear equation.
[MathLib] Fix a critical bug in GaussAlgorithm.

Reza discovered a bug within the gauss elimination.
[MathLib] DenseMatrix::write() print the matrix dims, too.
Merge pull request #419 from TomFischer/DenseMatrixReader

Bug fix for gauss algorithm