Improve recents kill all buttons behaviour

Adding programicaly set of margin for devices without HW keys and also respect UI.

PS7: Changed ImageView into ImageButton
PS8: Remove ugly background around icon

Change-Id: Ifd91e8a14d5f7eaaa05bc4958820b97ac6bf2e9c
Signed-off-by: kecinzer <kecinzer@gmail.com>