Zeiss ZVI: use coordinates to retrieve the correct plane

In some cases, the stored plane index will have nothing to do with the
stored ZCT coordinates.  The coordinates are more reliable, so we now
use those to retrieve the plane stream.
Fix tile indices for multi-series files
Merge pull request #405 from melissalinkert/rebased/dev_4_4/zvi-ordering

Zeiss ZVI: use coordinates to retrieve the correct plane (rebased onto dev_4_4)