Remove <gds2>, <gds21>, <gds22> with sensible names such as <grad_x_grad_x> and <grad_y_grad_y>.

[HanneThienpondt]

Note that the neoclassical terms and were implemented incorrectly because for clock-wise and counter clock-wise VMECs they would give very different results. And all other geometric quantities in stella are independent of the orientation of the magnetic field, as I assume they should be, except for a sign change. I changed them to the counter clock-wise values, since they seemed to be the most correct.