Add turn off action to WiFi Tether notification

PS 2+3 : Fixed Icon + Add persistence to WiFi state [mnazim]

Change-Id: I320405ed7e90e4c06ecdb127cd4c1cad6bedbcdd
Signed-off-by: Gergely Szell (sethyx) <szell@hu.ibm.com>

Conflicts:
	services/java/com/android/server/connectivity/Tethering.java

 Changes to be committed:
	modified:   core/res/res/values/slim_strings.xml
	modified:   core/res/res/values/slim_symbols.xml
	modified:   services/java/com/android/server/connectivity/Tethering.java