SystemBars: Allow the StatusBarComponent be externally defined

* The default UI for fugu is a TV with no statusbar, however we allow for a full android
    experience with a mouse and keyboard as well.
* Allow ro.cm.statusBarComponent=<component> be set in the build prop to enable the desired statubar.

* A HomeSwitcher is to be created for TvSettings and will also set the STATUSBAR_COMPONENT Settings.dB value,
     depending on if LeanbackLauncher or Trebuchet is the default.

* Order of preference of components:
      -> Prop
      -> Database (System.STATUSBAR_COMPONENT)
      -> config value

Change-Id: I8c0c9bccf9283960abd40b55a7c9ff47e3a97317
Signed-off-by: bmc08gt <brandon.mcansh@gmail.com>