Introduce the formulae hierarchy in order to extract all the
informations about formulae computation in a single visitor class.
Add the logical constraint that Height property is mandatory for nodes
in Netwon Raphson context.
Refactor the Vector and Matrix class removing the type parameter about
the type for the values stored in the vector or in the matrix.
Finish to test the Vector<>.minus method.
Merge remote-tracking branch 'origin/master'
Merging the README file