Zeiss ZVI: ignore invalid plane coordinates

If the parsed coordinates do not account for all of the images, then we
need to ignore them.  Otherwise, openBytes with different values of 'no'
may open the same image.

See http://www.openmicroscopy.org/community/posting.php?f=13&t=5130#pr10246
Merge pull request #544 from melissalinkert/zvi-coordinates

Zeiss ZVI: ignore invalid plane coordinates