Fix Sandcastle regression

`Sandcastle.addToolbarMenu` will make the first option a default if it has an `onselect` function and a default action is not already set.

This fixes a problem with the billboards and label examples where they were manually calling the first command and then it would get reset at the end of loading.
Merge pull request #1986 from AnalyticalGraphicsInc/fix-sandcastle

Fix Sandcastle regression