HALO notification should open in floating window mode

Change-Id: I9625bb505c78b361fcb618c7a3b23105568b8d5c
PS1: If HALO is activated all HALO notifications will open in floating window mode. If HALO is not activated notifications will open in mutiwimdow mode.
PS2: If HALO is activated "add to split view" in the recent application list will not be shown.
mutliwindow: notify split view if layout changed

Change-Id: I793b6d3dd05a5d1bbea178e646a1c6f14dec35c3
mutliwindow: notify split view if layout changed [2/2]

Change-Id: I2bbdd58dcf89cd70aa01a4c2bfc06641508f632c
multiwindow: Fix NullPointerException

Change-Id: I5c423bcde7d191331be53ce180f827e7023dc472