docs: Big update to action bar guide for ICS.

Added section for action provider, new APIs for handsets such as
split action bar, more information and diagrams for up navigation,
guidelines for picking action items, revised sample code and discussion
for tabs, add expandible action view info,
and expanded discussion for customizing action bar styles
bug:4726917

Change-Id: If61a5f2aad5ed21b0b23b3fc14309a50617f86ce