Gatan: adjust physical pixel sizes based upon the "Units" field

Fixes ticket #11509.
Flex: prevent NPE when filter data is missing

Fixes #11286.
Volocity: remove stacks that do not contain valid files

Fixes #11265.
Cellomics: fix handling of channels and analysis images

Channels are now detected correctly.  If the original file passed to
setId is a "d" channel (i.e. original image), then only "d" channels
will be included in the used file list.  If the file passed to setId is
an "o" channel (i.e. analysis results), then only "o" channels will be
included in the used file list.

Fixes #11148.
Zeiss CZI: fix Z size calculation

For linescans in particular, the Z size is stored in the 'size' field,
not the 'start' attribute.

Fixes ticket #11513.
FileStitcher: prevent readers from remaining open

This allows datasets with thousands of files to be opened without
causing the JVM to run out of file handles.

Fixes ticket #10971.
Cellomics: correct field index for single file datasets
Fix link to Homebrew Github repository
merge develop -D org -I include -E exclude: PR 528 (Tile performance improvements for VMS and NDPI)
merge develop -D org -I include -E exclude: PR 748 (Add support for Bio-Rad .scn files)
merge develop -D org -I include -E exclude: PR 767 (Fix Channel.Color interpretation in ImageJ)
merge develop -D org -I include -E exclude: PR 775 (Add JWlz to Ivy dependencies)
merge develop -D org -I include -E exclude: PR 777 (Various minor import fixes)
merge develop -D org -I include -E exclude: PR 778 (Fix link to Homebrew Github repository)