PEEK: configurable pickup timeout (1/2)

- Allow the user to set different pickup timeout when a notification comes up through PEEK.

Change-Id: Ifcd2f13101dcf6973ebcf016bce5f5314e1ce04c

Conflicts:
	core/java/android/provider/Settings.java
	packages/SystemUI/src/com/android/systemui/statusbar/notification/NotificationPeek.java

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