Improve Accessibility behaviour in recents

Currently accessibility services use the activity label that is also
displayed in recents, which can be very confusing as it does not
represent necessarily represent the app that the recent item is
running. To improve this we use a combination of the application label
and the activity label. The application label is also badged to
distinguish between different users.

Bug: 19688800
Change-Id: Ibead6c87767649aa11cf2fe086924a4b69bf187c