Richardson-Lucy deconvolution returns empty image for 16-bit input

I've been experimenting with the deconvolution ops and observed quite strange behavior of `RichardsonLucyF`/`RichardsonLucyTV`: when I call it with a 16-bit 3d image and a PSF, the op returns an empty image (all zeroes). It finally worked as expected when I converted the input image to `FloatType`. I think it'd be helpful to document it somewhere, or, even better, automatically convert the inputs to the expected type and then convert the result back to the original type.

Start with the RichardsonLucyF and RichardsonLucyTV entry points named in the issue and inspect how 16-bit and FloatType inputs are handled. Check existing deconvolution tests, if present, and define done as either documenting the required FloatType conversion or agreeing on and testing automatic conversion and result restoration; the issue names no files or tests.

Written by the indexing model from the issue text.