scivision/h5fortran: API breaking changes, allow overwrite data

%add => %write %get => %read

ierr is the last non-optional argument for every procedure. This allows making exception handler-like behavior in the end user program. Be sure to check the value of ierr, especially when writing files.

This paves the pathway to future slabbed / sliced read/write.

It's now possible to overwrite a variable with data of the same rank.