Enyo 2254: specified API for new onyx.TabBar - FOR REVIEW - DO NOT MERGE

Please review and comment the new TabBar API (see ENYO-2254 for more context).
Do not pay attention to the picker attached to the tab bar. This feature is far from being done, but it does not impact the API.

* ENYO-2254: use userId in resolveTab
* ENYO-2254: handle unique ID managed by user
* ENYO-2254: added next parameter to onTabChanged event
* ENYO-2254: added requestRemoveTab method (and corresponding event)
* ENYO-2254: fixed undef test
* ENYO-2254: replace alert with throw new Error
* ENYO-2254: added onTabRemoved event
* ENYO-2254: added activate method
* ENYO-2254: added user data placeheloder for addTab and onTabChanged event
* ENYO-2254: added removeTab method and added doc
* ENYO-2254: Spin TabBar out of TabPanels kind
* ENYO-1319: added a picker at the end of the scrolled tab bar
* ENYO-1319: added debug logs
* ENYO-1319: need to spell out the name of the Scroller component, otherwise, init will break

Enyo-DCO-1.1-Signed-off-by: Dominique Dumont <dominique.dumont@hp.com>