1. Addressed the UX comments: ActivityChooserView's default selection
popup no longer shows a message, rather hightlights the default
action which now it displays. Alignemnt of the UI.
2. The ShareActionProvider shows a sub-menu if the host item goes
on the overflow menu.
3. Now the heade layout of the activity chooser view is not needed hence
dropped and the item and footer ones are merged.
Change-Id: I0b3de623e4c0a805be9ed73a8541e66b8c00e2d2