BUILD_ISMRMRD (=OFF)

[rijobro]

It would be good to have an option to disable ismrmrd. This should then remove all of ISMRMRD's dependencies, e.g., HDF. (SIRF currently depends on HDF, but it should probably be ISMRMRD that depends on it. That way, when ISMRMRD is removed, HDF is also removed).

I could imagine this getting tricky. We don't want to compile MR-based SIRF code if ISMRMRD is disabled.