- introduce variables ngX_o2 = ngX/2 where X = p,j,z
- replace all ngX/2 call by a call to ngX_o2
- compiler should optimize it anyway but can we trust it?

checked sign of kxarray update when sheared

-1D routines development
-NL factor to correct moving grid method
-still an issue with the 1D r2c FFT
-ExB not working yet.

Better default input

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

to avoid /0 when P=0

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