New kernel order

[delandmeterp]

This is a major change!

Basically, the order of arguments is changed when interpolating a field.
Field[time, lon, lat, depth] becomes Field[time, depth, lat, lon]

To add some safety to this change, we removed the un-necessary dt arguments in kernel such that current kernels, that are likely interpolating fields using the old order, break.

But also, any interpolation outside a kernel can potentially break without previous notification.

Apart from checking the changes in the current PR, it is then also important to check what could have been forgotten in the code (for example, I had to modify some interpolation calls outside kernels)

[erikvansebille]

Large update; looks all good to me!