Slim Heads up: change behaviour of back key

Currently back key hides the heads up. We change it that the back key is still
working for the app which has focus and not for the heads up at all.

Reasons:

1. A lot user requested this due that they often hide the heads up during they work
   on the phone, simply due that the back button is often pressed on a normal workflow.
   The results is indeed that a lot heads up windows are missed excidentaly.

2. First I thought to make it optional. But there is another big reason to do it this way. Current
   behaviour is that the heads up view gets focus...and that we dispatch the back key only. Thing is
   that other key events are still rooted to the heads up window. Well most things a user will not see.
   But eg on apps with input field some keys on the IME keyboard do not work during the heads up is showing
   which is a big no go when we assume that heads up needs to be as much non intrusive as possible.

That being said we remove the dispatch override and give the heads up window FLAG_NOT_FOCUSABLE flag
which will bypass any key events to the window behind which had focus before the heads up showed up.

FLAG_NOT_TOUCH_MODAL we can remove due that FLAG_NOT_FOCUSABLE automatically enables the FLAG_NOT_TOUCH_MODAL flag.

Change-Id: Ied4c7d2dd5b99f89af958f01db980a36d431bbc3
HeadsUp: Only remove heads up if attached to window

Attempting to remove mHeadsUpNoficiationView from the window manager
when it is not currently attached will throw an IllegalArgumentException
so we check if it is attached and if so remove it, otherwise carry on.

As well remove possible left children in statusbarview

Change-Id: Ida916eba496c4183e47288ef24a8a93c46a7eddf
SystemUI: improve one finger notification expansion

Sometimes the quick settings ribbon would eat the initial ACTION_DOWN
setting mInitialTouchY in the expand helper, but we are clearly not in a
notification that we can expand here. So only set the initial y point if
we are inside the notification scrollview.

Change-Id: I628553ac15cc6b4ee3c682fe46bd1d96c6bc154d
HeadsUp: Correctly add and remove the window

isAttachedToWindow() basically works to determine if the view was attached or not.

But on the boot up process when already addHeadsUpView is called but the system is not
fully up and a recreation happens (eg on TRDS...due that the UIModeManager is doing its work as soon as system is ready)
the view gets attached....but not removed on the recreation due that at this time isAttachedToWindow() will return false even though the
window was added.

To solve simply use a boolean instead of isAttachedToWindow()

Change-Id: Ib576a83cadc581683f2a5b0afc922c53b01888b7
fb: Show heads up at the bottom of the screen (1/2)

Due of user requests and indeed especially on hw key devices for a better
workflow we add an option to show heads up notifications on the bottom instead
of the top.

Animation we leave as is due that if it slide from the bottom into the screen it happens
to often that the user accidentaly interacts with it. If it comes from the top of the
container we add, the user has enough time to realize it. Sometimes a ms can make a big difference.

As well this commit fixes the wrong gap on the top if user boots up directly
into immersive mode.

PS:
- if IME keyboard is showing show the heads up on the top to do not disturb the typing.
PS:
- NPE if updatePosition is called to early from the system.

Change-Id: Iea7fbe466808531a9351cf4048570b8f56eb698e

Conflicts:
	packages/SystemUI/src/com/android/systemui/statusbar/phone/PhoneStatusBar.java