Issue 6501: "Search" application stops when entering its settings

QuickSearchBox is missing declared class com.android.quicksearchbox.preferences.SearchableItemsActivity
since ics and jb.
This changes add this class, use the existings headers, and redirect to SearchableItemsFragment when
user click in the settings icon of the search bar.

Patchset 2: Fixed comment header

Cherry-Pick: http://review.cyanogenmod.org/#/c/26421/2

Change-Id: Icd616492c1fa4dd6342e4983865530c7b9e1a037