Display options: allow configuration of wake on plug behavior (2/2)

The PowerManager now checks Settings.Global.WAKE_WHEN_PLUGGED_OR_UNPLUGGED
to determine wake-on-plug behavior instead of using the configuration option
config_unplugTurnsOnScreen.

PS 2: Re-added config_unplugTurnsOnScreen, which is used as the default value
for the new setting.

PS 3: Fix white-space error

PS 4: Fix white-space error

Change-Id: I062794828831a2b6faf4293579103d2251f1bdd0