make bezierBasis independant from declaration of element tag in GmshDefines.
move static methods getTag(..) & **FromTag(..) from MElement to ElementType.
completely revert to double for monomials.

Monomials order changed !
Points of Prism p>2 changed !
3D Serendipity elements have now nodes only on edges !

Modify gmshGeneratePoints.
All validated.

Warning : Points for high order prisms will change ! Old version is incoherent with what is done with other elements 

Goal: at the end, have only one algo for generation of Points/Monomials/Exponents/.. per element

Implementation of high order pyramids. Introduces nodalBasis as a parent class of polynomialBasis and pyramidalBasis.