refactor: use ItemNavigation optimally

[vladitasev]

This change refactors the usage of ItemNavigation.js for all components except date/time related ones (which will be addressed separately).

Changes:

• Now that getItemsCallback can be set in the constructor, this is the preferable way of passing it. This also eliminates the need of a separate initItemNavigation function that many components had as they needed 2 lines of code - new ItemNavigation and to set the callback.
• Implement the focusin event for Timeline.js as it did not update the item navigation like the rest of the components whenever the user clicks with the mouse.
• Do not use ItemNavigation.prototype.current any more (it is marked as deprecated). Always call update instead.
• Do not use ItemNavigation.prototype.currentIndex any more (it is private). Always call update instead.
• Do not use ItemNavigation.prototype.focusCurrent any more (marked as deprecated). Use the item that was passed to update directly (see Tokenizer.js for example).
• Do not re-initialize getItemsCallback in onBeforeRendering - it is a callback exactly for the reason that based on the state of the component, it may return completely different data (see AvatarGroup.js for an example)

Summary:

• Initialize ItemNavigation in the constructor of the component and pass the callback there
• Implement a focusin event for your component and call update with the newly focused item to synchronize the item navigation. Do not use current or currentIndex.