Update on sending a.u.t. to background functionality

Changed the way the application is sent to background. Now the home screen is opened, instead of the activities task being directly moved back. This is what would happen if the user were to hit the "Home" key on his/her device.

Also added a proper BackgroundAppTest in the selendroid test app.


want to move this line to a private method, better to not have the code duplication of this line