SystemUI: temporary workaround for garbeled screenshot preview

The problem shows some underlying issues View.LAYER_TYPE_HARDWARE
so this is NOT a fix. Just since this issue is so obvious visible
it would save us from a lot of bug reports and questions for now :)

Change-Id: If188aa668c1024e857d931ccef4ad3e99edce348
[WIP] Multi-window

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] SystemUI: Pull down QS if x > 85% width

Added Settings

Change-Id: Ic41d331e8f0166484b124e91a8ed8e904ff38edb