[1/2] SystemUI: Allow to include / exclude cached apps ram usage in recents

allows to include / exclude cached apps in the ram usage bar in recents
some people went like "WTF, SO LESS RAMZ WITH YOUR ROM!"

so lets satisfy them and add an toggle to include / exclude cached apps.
by default it excludes them.

Change-Id: Icf35d36c422a1046c7cb9289dad1ed99b82de8d0