-kx is now 2D (ky dependant)
-kperp^2 array for computation reduction
-routines to update the grids

The perpendicular pressure effects are already added above
so this commented part is useles

avoid incoherent value in terminal

 in restart now

to avoid /0 when P=0

+ explanation of the structure

for adaptive time stepping
and cleaning

Cyq0_x0 variable
compute jacobian and curvatures using contra gij
shear=0 is set in Z-pinch

gather real xyz array

kx grid uses now the Cyq0_x0 factor
grid module init first the indices