Status bar Auto-Hide [1/2]

Add an option to auto-hide status bar when there are no
notifications.

PS 2 : Improved Logic

Change-Id: I9f9fdb443f6ed981c1941716491cef757b42f8ba

Conflicts:
	core/java/android/provider/Settings.java
	packages/SystemUI/src/com/android/systemui/statusbar/phone/PhoneStatusBar.java
	policy/src/com/android/internal/policy/impl/PhoneWindowManager.java
Frameworks: Ehance toggleNotificationShade feature

allows to toggle notification drawer in any situations
on fullscreen mode as well in expanded desktop mode
and on all other features we have
cheers

Change-Id: I56185f2c48700d9f2d69c02585810db4e95e2e32

Conflicts:
	core/java/android/provider/Settings.java
	packages/SystemUI/src/com/android/systemui/statusbar/phone/PhoneStatusBarView.java
	policy/src/com/android/internal/policy/impl/PhoneWindowManager.java

Conflicts:
	core/java/android/provider/Settings.java