add constructor taking sparsity in LisLinearSystem
add DenseLinearSystem (in progress)
LisLinearSystem should be inherited from ISystemOfLinearEquations
complete DenseLinearSystem. testing it is not done yet
add sparsity object as a parameter for constructor in DenseLinearSystem
implement printout() in DenseLinearSystem
Initialize global matrix on creation.

Fixes a bug occuring randomly depending on memory content.
correct path
add helper functions to release memory
add DiscreteLib in CMake
add TestDiscreteLib
save progress in DiscreteLib
need to include some other headers
add DiscreteLib in Doxyfile
link GeoLib to MathLib
save progress in DiscreteLib
save
add DoF object
save progress. Test cases are working
Remove extra namespace specialization.