[WIP] Multi-window

[[[ USE PS 18 IF YOU WANT TO TEST - WORK IN PROGRESS ]]]

This is a big work in progress, which currently has some bugs,
but begins to look okay.

You can already multitask a little bit, by using the
app switcher and long-pressing an icon, then select "Add to
Split View".
Last window touched gets the key focus.

Code is very ugly, I know. Don't merge it, don't use it
for now. Unless you want to make your code ugly.

Enjoy :)

Change-Id: I4a03a84539fd3ac1273f0d3503fe8fafcd16be26
[1/2] Base: Lockscreen Notifications

PS11:
    Lockscreen Notifications: several fixes

    - fix notification not responding when removed and added in a short period of time (e.g. gravity screen start/stop)
    - just unlock screen on notification click when there's an activity to start
    - fix notification hide animation
    - just wake screen on reposted notifications when it's not ongoing (wake on notification before made the device stay awake for ever when a download/countdown or something similiar was running)

PS12/13:
    Lockscreen Notifications: Bring inline with AOSPAL implementation
    Lockscreen Notifications: Fix possible NPE
    [1/2 ]Lockscreen Notifications: make offset top user configurable & add privacy mode
    Lockscreen Notifications: Copyright
    Lockscreen Notifications: just scroll down in "showAllNotifications"

PS14:
    Lockscreen Notifications: Fix recognizing of settings update

PS15:
    Lockscreen Notifications: make width dynamic (WRAP_CONTENT)

PS16:
    Lockscreen Notifications: make animations a bit faster

Change-Id: I342b9fa6266c4c64f04121a8a2938de6532082b4