Minor fixes

[totork]

Here are some changes that came up while running the code

1. -Importing the TCV X-21 field gave me an error of different dimensions of psi, changing the way psi is handled in the GEQDSK fixed this and enables using such files for the magnetic field
2. Using By for the area calculation can lead to negative field strengths depending on the orientation and hence negative surface areas. Also to preserve magnetic flux, the magnitude should be used I think?
3. Add dapg to be run by default, otherwise grids miss this and the start of the simulation throws an error.
4. Added chunking in X direction