Refactored the layout of a notifications

Notifications now consist of ExpandableViews instead of SizeAdaptiveLayouts
to avoid layout passes during the resizing. The StackScrollAlgorithm and its
States are also refactored in order to support the new behaviour. In addition,
the generation of the outline is moved to the notification views instead of
the container which contains them.

Change-Id: I1ac1292a6520f5951610039bfa204c204be9d640