Linalg cleanup

Linalg cleanup includes : 
- generic version of mcsne on cpu with no loss of performance 
- added optimized triangular solver
- removed functions based on the old model
- modified linsolve with terminal macros and added mcsne
- trans node is recognized through linsolve

Can now solve a triangular system this way : 
nt2::table<T, nt2::upper_triangular> x; 
x = nt2::linsolve(a,x);
x = nt2::linsolve(nt2::trans(a),x);

Can now solve a linear system using semi normal equations with a tall and skinny :  
x = nt2::linsolve(a,b, nt2::fast_);