Use tab key to reach the tab. Once a tab has focus use:
left and right arrows to move from tab to tab. Panel is made visible when tab gets focus. Arrow keys do not cycle around the tabs
ctrl-left and ctrl-right arrows behave the same as left and right arrows
ctrl-shift-pageup / ctrl-shift-pagedown is the same as left and right arrows but WILL cycle around the tab order (shift was added as a modifier
so as not to conflict with the Firefox tabbing keys and the WindowEyes keys)
I did not implement ctrl-shift-tab /ctrl-tab since these keys conflict with the Firefox tabbing keys.