Recents: Launch as Floating App

Ported from JB 4.3
Based on hybrid (Aaron) and Halo (Jesus) implementation

AICP'fied. Strings already defined in res/values/strings_custom.xml

Signed-off-by: Alexis Rico <sferadev@gmail.com>
Change-Id: I84f4d3928af5c6ddd96a9a173a1c24e85ff606dd