nc units

we need to change the unit definitions in nc output to conform udunits. nv can't undertand our definitions

udunits: unknown units for northing: "m or degrees_north"

Set here: https://git.ufz.de/mhm/mhm/-/blob/7d970434ca7950b0b14bef2a00bcc57bb3c0cc1f/src/mHM/mo_write_fluxes_states.f90#L864