Reduce duplication of 1d base state -> 3d MultiFab calculations

[harpolea]

Routines offloaded to the GPU now take the 1d base state mapped to a 3d MultiFab. This mapping is often done within the C++ wrapper function of these routines, which is likely to lead to lots of duplication, the same quantities being mapped repeatedly by different functions. It might be more efficient to do the mapping once (e.g. just after the base state is changed) and carrying this around rather than computing it on the fly every time it's needed.