Prepare for removal of dual viewer/canvas object

[ejeschke]

• updates all example programs to avoid using the combination object
• will allow us to make #973 a smaller PR
• this doesn't actually deprecate anything

[ejeschke]

When you have time, @pllim. This is just updating example programs and introduces no feature changes to reference viewer or any deprecations.

[pllim]

"This branch has conflicts that must be resolved" -- You might want to rebase.

[ejeschke]

Thanks, @pllim! Merging.