Split view merged 10109

Fixes a couple of bugs in Figure scripts. To test:

 - Run the 'Split View Figure' from the custom UI in Insight (under 'Publishing Options') using a multi-channel image. Turn off some channels for the right-hand (merged) panel. See that your choice is reflected in the figure (Bug was that all channels were still on)
 - Run Split_View_Figure and ROI_Split_Figure from the Scripts menu (script-generated UI) and for each one, fill in the "Merged Colours" key:value pair of fields with 0 and 255. The script should complete and you'll have a single blue channel in the merged Image of the figure.
 - Repeat this, entering non-number strings into the Merged Colours fields. The scripts should still generate a figure, with warnings appearing in the 'Info' output.