Tidying ITK user doc page
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 796 (Zip: improve reader and handle performance)
merge develop -D org -I include -E exclude: PR 804 (Leica LIF: 'C' goes before other dimensions if SizeC and SizeT > 1)
merge develop -D org -I include -E exclude: PR 807 (CellWorx: ignore thumbnails and missing channel names (rebased onto develop))
merge develop -D org -I include -E exclude: PR 809 (Tidying ITK user doc page)