LockScreen: add option to minimize challenge when showing the lockscreen (2/2)

This will allow the user to choose wether the lockscreen
challenge (circle, pattern, pin) is minimized when the screen
is turned on.

PS2: hide option on tablets - needs http://gerrit.sudoservers.com/4754
PS3: rebase
PS4: properly hide on tablets

Signed-off-by: Dirk Rettschlag <dirk.rettschlag@gmail.com>
Signed-off-by: KhasMek <Boushh@gmail.com>
Change-Id: I3a95ca0c05092286e66855df73d47e4f32308463