Extend BMI interface

[ahmad-el-sayed]

No description provided.

[Peter9192]

I tried building the docker container from this branch, but it appears to be broken due to recent changes in sfincs_infiltration. Do you think this is easy to fix, or could we rebase the changes from this PR onto https://github.com/Deltares/SFINCS/tree/a5136da72ad48e562dbaeba5ade2a9007f6c75c0 (I can confirm the docker build still worked there)?

[Peter9192]

Thanks a lot for all the work put into this! After struggling for some time I was able to use most of the new BMI functionality.

Main thing that didn't work as expected was the get_values implementation. I suggested a (partial) fix in #57. Another source of confusion was the grid type, it returned 'rectilinear', but that, in combination with grid_rank=2 suggests that grid_size = shape[0]*shape[1]. I changed it to always return unstructured in #57.

Finally a small note that update_until in the bmi spec gets the new target time, rather than the dt, as argument.

I've listed a few notes here