Slidebook TIFF: prevent NPEs when metadata is missing
Slidebook TIFF: close open file handle in TiffParser
PNG: fix support for images with fewer than 8 bits per pixel

Fixes #10887.
Metamorph TIFF: populate PhysicalSizeZ

Fixes #10884.
Leica LIF: parse PhysicalSizeZ from one more place

Fixes #10843.
DNG: fix type checking to prevent picking up Photoshop files
SimplePCI: better calculation of Z/T dimensions

Conflicts:

	components/bio-formats/src/loci/formats/in/PCIReader.java
SimplePCI: do not populate more timestamps than planes
SVS: disable file grouping

It's very common to have similarly-named files in the same directory
that have very different dimensions.  To prevent weird problems with grouping,
and because the workflow of dealing with slides means that grouping
isn't really necessary, it is now disabled.
Slidebook TIFF: make type checking more rigorous
CellWorx: do not pick up .pnl/.tiff files if file grouping is turned off

Noticed by Stéphane Dallongeville.
Leica LIF: a few more physical size and position fixes

Noticed by Olivier Burri:

http://www.openmicroscopy.org/community/viewtopic.php?f=13&t=4710#p9964
Merge remote-tracking branch 'origin/develop' into may-bug-fixes

Conflicts:
	components/bio-formats/src/loci/formats/in/SlidebookTiffReader.java
merge develop -D org -I include -E exclude: PR 512 (xsd-fu: Extend C++ support to generate headers and include guards)
merge develop -D org -I include -E exclude: PR 518 (ScanR: clear the pixel buffer when an invalid TIFF is found (rebased onto develop))
merge develop -D org -I include -E exclude: PR 519 (.cxd dimension detection fixes (rebased onto develop))
merge develop -D org -I include -E exclude: PR 521 (Assorted bug fixes for May)