Rendering settings unification

This PR replaces the original PR gh-3005. @dominikl is away
This PR only fixes a NPE noticed by @gusferguson see https://github.com/openmicroscopy/openmicroscopy/pull/3005#issuecomment-55589012

To test: 
*  Moved through images in a dataset using up-down arrows to check ROI counts. 
* Double-clicked on image to open in full viewer. No Crash