Migrate to new WM.LP.flags based translucent decor API.

Update/rename common helper class TranslucentDecor to handle both
apis so behavior is correct on old and new builds.

Bug:10674960
Change-Id: Id3b2d523026e9e4f2f71f0eab404792207c6d8c7
Smooth out slide in/out animation for the overview panel

Change-Id: I742d2248b7cf70767f9e776d88db6fc1aaa767ce
Trebuchet: launch framework WallpaperPicker

After long pressing on the home screen and selecting "Wallpapers"
Trebuchet's activity was being called.

We have now switched to framework's WallpaperPicker activity, so open
that one instead.

Change-Id: I97165350f1b995ae921eebbc126eb3e0e2396963
Signed-off-by: Roman Birg <roman@cyngn.com>