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>
Fixing issues introduced in 31cc95a0:
 - HotSeat needs go visible/invisible when transitioning in and out of overview mode
 - Animation listener for setting alphas needs to remove itself when the animation finishes

Change-Id: I654c0e700c9bc3f77692ed653f8158cec1f2430b
Merge remote-tracking branch 'cm/cm-11.0' into cm-11.0