Add Q4 to Gauss Quadrature and allow Gauss point number overwride
Add Q4 to Gauss Quadrature and allow Gauss point number overwride

Q4 can now be calculated using the get_gauss() method of the Element class.

It is now possible to overwride the calculated Gauss point number (npg) when using the get_gauss() method. This can prove useful when trying to assess higher order equations.
MrJarv1s/FEMur