Enable/disable navigation bar on the fly, without reboot (Confirmed working)

Based on two of these commits:

https://github.com/AOSPAL/android_frameworks_base/commit/64f1b159943d4dbb42c67ae803c283df2a8bd857
https://github.com/VanirAOSP/frameworks_base/commit/5583cd9ab2b8b3d89b777c129c5b4f3a43f7cdbe#diff-545751e92b455f9bb5d1775185e6f296R230