Stop populating RemoteViews in Notifications.

Builder now stores its parameters directly in the
Notification object itself, reducing the amount of copying
needed to construct the final Notification as well as
converging the two data structures. All Builder data is now
captured in Notification, so it is easy to reconstruct
a Builder for any Notification object.

This obviates all stripping/unstripping operations because
all Notification objects start life "stripped" of their
RemoteViews, which must be constructed explicitly by clients
(presumably listeners wishing to show the notification to
the user in its conventional form).

Note: While contentView, bigContentView, and
headsUpContentView are being @Deprecated in this CL,
specifying custom RemoteViews is definitely still supported!
You just have to use Builder methods to do so.

Bug: 20153922
Change-Id: I81f8ffed0eb76084b2f2b25b97e325858f0a1d05