BDV export doesn't support float32 images

[karlduderstadt]

While the Mars Rovers BDV supports displaying combinations of uint16 and float32, molecule export fails in the case where there is a float32 source mixed with uint16. Interestingly, if you only have a float32 source export works. Since there was no error message generated, it seems like the issue might result for uiService.show not being able to display mixed ImgPlus objects.

The simplest solution should be to maybe force the exported type for sources to float32 in case there is one source with float32 type. Another option could be to somehow update the uiService.show to support the type created when there is a mixture. However, this is probably a limitation of ImagePlus objects. I think they only support one type and not mixed types.

There is also some kind of error generated when exporting a single source. Will investigate and update the specifics.

[karlduderstadt]

When there is only one source this error is returned. Need to have a special case for that...