TIFF: correct for invalid tile heights
merge develop -D org -I include -E exclude: PR 159 (Improve .ndpi support)
merge develop -D org -I include -E exclude: PR 351 (Add SPW support to FakeReader)
merge develop -D org -I include -E exclude: PR 424 (Specification changes for 2013-06 release)
merge develop -D org -I include -E exclude: PR 435 (Fixes for March 2013 bug week (rebased onto develop))
merge develop -D org -I include -E exclude: PR 438 (Fix the autogenerated metadata field counts (rebased onto develop))