systemui: Fix various issues with transparent bars

 * You current can't enable lights-out with transparency/translucency-
   the code is only half-way there but it's sequenced in a strange way
   and the translucent combo isn't implemented at all. Fix it.
 * Enabling a transparent navbar when the bar is vertical (landscape)
   has bugs that make the behavior unpredictable for some apps. We can
   still allow it, so add a new View flag to signal this.

Change-Id: Iec98c960d6c13a294d8f9f0dd9f9e2fc1f8f9b52