Sfincs BMI incomplete

[Peter9192]

This package depends on the BMI functions provided in https://github.com/Deltares/SFINCS/blob/v2.0.2_Blockhaus_release/source/src/sfincs_bmi.f90. However, this is a very incomplete implementation of the basic modelling interface. The full bmi fortran spec is documented here. Most of these functions are missing, some of them are named differently, and one of them is not exported.

For coupling with wflow through BMI, we need at least the subset of BMI functions used by eWaterCycle, which are documentated here. These functions are used to identify grid cell indices corresponding to a certain coordinate, setting and getting the state at these indices, et cetera.