r48513: added 'accesskey' attribute support to ace:breadcrumbMenu, ace:column, ace:dataTable paginator, ace:rowEditor, ace:fileEntry, ace:richTextEntry, ace:sliderEntry, and ace:tabPane; also made all ace:tabSet tab headers focusable and navigable via the tab key

After reviewing the current implementation I've got some concerns.

Specifically, changing the tabs using the Tab key is not a good idea as it prevents the user from using the keyboard to enter the selected tabPane contents (via Tab). Since pressing Tab switches the currently selected Tab (as does the left/right/up/dwn arrows), there is no way to navigate to the tabPane contents via the keyboard.

The ARIA recommendations for keyboard nav. within a complex component would suggest that we should use the left/right arrow keys to navigate between the tabs, and leave Tab to continue through the tab-order, thus allowing the user to tab into the contents of the selected tabPane.

r48623: modified keyboard navigation support in this way: pressing tab will transfer focus to the first focusable element in the pane's body; only the arrow keys, home and end will transfer focus to another tab header if a tab currently has focus, and it will be activated only by pressing space

Verified ICEfaces4 trunk r48629, using QA tabSet test app, /tabSetOnly.jsf test page, on IE8, IE11, FF41, Chrome50.
Verified showcase > tabSet tests on FF41.