Arrange to create a 2d PFSA file for each 3d PFSB file

The hxActor currently writes PFSB files only: the full ramp. We have planned to also write PFSA files: single image versions reduced from the full stack.

Note that we never settled on exactly what to write. A reality is that the DAQ BEEs most certainly do not have enough CPU or RAM to compute more than lastRead-firstRead (or the only read), so that's what we start with.

One concern is that "A" files from Subaru could be seen as the "correct" raw instrument files, just from past convention. I'll state that any proper 3d-to-2d reduction is almost certain to evolve, so there might never be a dependably stable science-grade 2d product: it will always depend on a particular version of the 2D DRP pipeline. [ Besides, any good reduction will come with (at least) both variance and mask images. ]

I suppose we could call any such quick raw 2d reductions something other than "PFSA" files, and simply not write "PFSA" files for the NIR arms?

rhl, Hisanori Furusawa, eric