[1/2] Base: Hide power menu on lockscreen

Adds an option to enable/disable power menu on lockscreen.

Settings: https://gerrit.omnirom.org/#/c/4702/

Change-Id: I0de1501d0ecedb7b9b08fbb3aebaecd0e63cc09e
Signed-off-by: bart452 <bart4524@gmail.com>
Merge "[1/2] Base: Hide power menu on lockscreen" into kk44