[Base] Nav bar tweaks

    - Toggle on/off (CyanogenMod alredy did but only for hw keys devices). crDroid allow all devices to do that for those using PIE apps.
    - Nav bar dimensions (height and width)
    - Here we also automatically reverts CyanogenMod navbar toggle: https://github.com/crdroidandroid/android_frameworks_base/commit/b70cda7d0d9b5142f54d390275b5e2ffa64ae9b4

    PS: THIS COMMIT IS A SQUASHED PORTED FROM crDroid KK and 99% od the codes are from SlimRoms.