[Gmsh] Change coordinate of a vertex in a GModel using API

[Agnese, Marco]

Hello GMSH users,
I have a GModel and I want to change the coordinates of a point inside it: just the coordinates of a point , everything in the GModel need to remains exactly the same. 
Is there a way without creating from scratch a new GModel?
Because if I extract the pointer to a GVertex with the method getVertexByTag I have a const pointer therefore I cannot modify the value but only read it. 
Is there a method to have a non const pointer? Or is there  a method to simply change the coordinates?

Thank you,
cheers,
Marco Agnese.