COMP: convert to integer explicitly to avoid ambiguity

Fixes #3420


git-svn-id: http://svn.slicer.org/Slicer4/trunk@22528 3bd1e089-480b-0410-8dfb-8563597acbee
STYLE: fix the grey slice viewers labels to be distinctive

Per comment from Jim, see issue 2384


git-svn-id: http://svn.slicer.org/Slicer4/trunk@22529 3bd1e089-480b-0410-8dfb-8563597acbee
BUG: fix the numbering of slice viewer labels

In the situations when Yellow/Green/Red viewers are present, the additional viewers should be numbered starting from 4.


git-svn-id: http://svn.slicer.org/Slicer4/trunk@22530 3bd1e089-480b-0410-8dfb-8563597acbee