Photoshop TIFF: fix offset to first layer

Fixes #10203.
Fixing broken OME docs link & adding git hyperlink
Merge pull request #347 from melissalinkert/rebased/develop/10203

Photoshop TIFF: fix offset to first layer (rebased onto develop)
Merge pull request #350 from hflynn/rebased/develop/link-fix

Fixing broken OME docs link & adding git hyperlink (rebased onto develop)