Settings: Don't show protected apps options in restricted profiles.

Change-Id: I38c2e8fd3508d360f0e23703ce6c939f02f3714e
JIRA: 4668
Issue: https://jira.cyanogenmod.org/browse/CYAN-4668
(cherry picked from commit 005d167816bca21791de7ea261aa37b1341fa3ff)
Settings: don't remove navigation bar prefs when toggling

For devices which support the KeyDisabler class, toggling the nav bar
removes the navigation bar category, but does not add it back. If a
device can have the nav bar toggled, don't remove the category, but just
disable/enable it.

Change-Id: Ie527e3eb357e4a46097257d90c07c78e61f043a9
Signed-off-by: Roman Birg <roman@cyngn.com>
(cherry picked from commit 34344a5fa2a03d849901f09340f3dd8010e2a7fe)
Settings: Only show clear button when search field has text.

Change-Id: I69bf6a31a933459be2c652434aec412105395dcc
(cherry picked from commit 8a8c4c1e1b916f9650961bf4390a17de7619642e)
Cleanup.

Now that button and keyboard backlight don't use the HW framework
anymore, there's no point in having an abstraction for a single use case.

Change-Id: Ib66b2a29a105d53e3ba4273abb06977b132c1fc8
(cherry picked from commit b2948d10398bd3ebc2ce469b09d7660106db1277)