Auto-expand pages in Options dialog.

It's incredibly annoying that the names of pages in the Settings/View Settings
dialog are not expanded by default. This fixes it. We now expand the tree widget
showing the names of the pages available when new pages are added to the dialog.

Change-Id: Id2440f2f26e9b5ceeb2fbd4ecae3b8cf5c059af0
Merge topic '13818_fix_plot_min_max' into next

3094be4 Auto-expand pages in Options dialog.