Updated Nexus imprint screen

The fingerprint settings screen looked ugly so an
icon was added and the styles used in the
preferences normalized so everything lines up
and is flush now.

Test: Visually Inspect
Bug: 27834731
Change-Id: I208d7fc2aecbe64d3a0b771fc73f49c9612f6efa
(cherry picked from commit 3d2d5e04)