changing tabs via keyboard does not work when focus is within a stack container pane

[Becky Gibson]

Using ctrl-tab/ctrl-shift-tab and ctrl-pageup/pagedown does not work to move to the next stack container tab when focus is within a stack container pane. This DOES work for tab containers so hopefully it is an easy fix. If not, we can push this to 1.1 as long as the stack container doc is updated to indicate where focus must be in order for the ctrl-pageup/pagedown keys to work.

Note that I updated test_stackContainer.html to include a link in the content of page 2 so there is something focusable in one of the panes.

[Becky Gibson]

(In [10788]) refs #4697. Added a focusable element into one of the pages of the stack container to test keyboard behavior when focus is within a pane.

[davidb]

We need to add a keypress handler to the StackContainer?.... looking.

[davidb]

this makes it work in the test but i wonder if we want to auto add this somehow?

[davidb]

(In [10876]) Fixes #4697, connected onkeypress with container base handler function.

[davidb]

(In [10877]) Refs #4697, onkeypress now connected in superclass

[davidb]

(In [10879]) Refs #4697, onkeypress now connected in superclass